Etching method, semiconductor and fabricating method for the same

ABSTRACT

An organic/inorganic hybrid film represented by SiC x H y O z  (x&gt;0, y≧0, z&gt;0) is plasma-etched with an etching gas containing fluorine, carbon and nitrogen. During the etching, a carbon component is eliminated from the surface portion of the organic/inorganic hybrid film due to the existence of the nitrogen in the etching gas, to thereby reform the surface portion. The reformed surface portion is nicely plasma-etched with the etching gas containing fluorine and carbon.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a method for etching anorganic/inorganic hybrid film represented by SiC_(x)H_(y)O_(z) (x>0,y≧0, z>0), a semiconductor device having an interlayer insulating filmmade of the organic/inorganic hybrid film, and a fabricating method forsuch a semiconductor device.

[0002] Recent semiconductor integrated circuit devices adopt multilayerinterconnection structures to meet requests for size scale-down andhigher integration. Conventionally, a silicon oxide (SiO₂) film has beenused as an interlayer insulating film provided between lowerinterconnections and upper interconnections. Contact holes are formedthrough such an interlayer insulating film by plasma etching forconnection with lower interconnections when a multilayer interconnectionstructure is adopted.

[0003] Hereinafter, as a first conventional example, an etching methodfor formation of contact holes through an interlayer insulating filmmade of a silicon oxide film will be described with reference to FIGS.22(a) to 22(d).

[0004] First, as shown in FIG. 22(a), a lower interconnection 12 made ofcopper, for example, is formed in an insulating film 11 deposited on asemiconductor substrate 10 by a known method. On the lowerinterconnection 12, deposited is an etching stopper film 13 made of asilicon nitride (Si₃N₄) film, for example, that has the function ofpreventing the lower interconnection 12 from oxidizing during etchingand also stopping the etching. An interlayer insulating film 14 made ofa silicon oxide (SiO₂) film is deposited on the etching stopper film 13.A resist pattern 15 having an opening for formation of a contact hole isthen formed on the interlayer insulating film 14. Note that, althoughillustration is omitted, the sides and the bottom of the lowerinterconnection 12 are normally coated with barrier metal.

[0005] Thereafter, as shown in FIG. 22(b), a contact hole 16 is formedthrough the interlayer insulating film 14 using the resist pattern 15 asa mask by plasma etching with an etching gas containing fluorine andcarbon, such as CF₄ gas, C₂F₆ gas, C₃F₈ gas, CHF₃ gas, C₃F₈ gas, or C₄F₈gas.

[0006] As shown in FIG. 22(c), the resist pattern 15 is removed byashing with oxygen plasma. As shown in FIG. 22(d), the portion of theetching stopper layer 13 exposed in the contact hole 16 is removed.

[0007] In recent years, further scale-down and higher integration ofmultilayer interconnection structures have been demanded, and withrealization of this demand, signal delay at interconnections has becomegreatly influential to the operation speed of a semiconductor integratedcircuit.

[0008] In order to reduce signal delay at interconnections, it has beenproposed to use a film having a low dielectric constant (e=2 to 3) asthe interlayer insulating film. As such a film having a low dielectricconstant, known are an organic insulating film containing an organiccompound as a main component, a fluorine-containing insulating film madeof a fluorine-containing silicon oxide (SiOF), and an organic/inorganichybrid film represented by SiC_(x)H_(y)O_(z) (x>b 0, y≧0, z>0). JapaneseLaid-Open Patent Publication No. 10-125674 proposes an organic/inorganichybrid film made of a silicon oxide film containing carbon and hydrogen,deposited by feeding hexamethyldisiloxane (HMDSO) as a material gas.

[0009] The organic insulating film, of which the composition is similarto that of a resist film, has the following problem. When a resistpattern formed on the organic insulating film is to be removed by ashingwith oxygen plasma, the organic insulating film itself is damaged by theoxygen plasma. The fluorine-containing insulating film has the problemthat it easily comes off due to its poor adhesion to an underlying filmand also it is poor in mechanical strength and heat resistance.

[0010] The organic/inorganic hybrid film has a specific dielectricconstant considerably smaller than the fluorine-containing insulatingfilm and has a mechanical strength roughly equal to that of thefluorine-containing insulating film. Moreover, the organic/inorganichybrid film, of which the composition is not similar to that of a resistfilm, is less damaged by oxygen plasma, and therefore, the resistpattern can be removed by ashing with oxygen plasma.

[0011] In consideration of the above, the organic/inorganic hybrid filmis promising as an interlayer insulating film having a low specificdielectric constant.

[0012] With the recent demand for size scale-down and higher integrationof semiconductor integrated circuit devices, also, the diameter ofcontact holes formed through the interlayer insulating film has becomefiner and the aspect ratio of the contact holes has become larger. It isdifficult to fill such fine contact holes having a large aspect ratiowith a conductive material with reliability.

[0013] To solve the above problem, Japanese Laid-Open Patent PublicationNo. 8-191062, for example, proposes a technique in which the diameter ofthe contact holes is made larger near the opening thereof than near thebottom thereof, to facilitate filling of the contact holes with aconductive material.

[0014] Hereinafter, as the second conventional example, the etchingmethod disclosed in Japanese Laid-Open Patent Publication No. 8-191062will be described with reference to FIGS. 23(a) to 23(d). Note that inFIGS. 23(a) to 23(d), illustration of a lower interconnection isomitted.

[0015] First, as shown in FIG. 23(a), a resist pattern 15 having anopening 15 a for formation of a contact hole is formed on an interlayerinsulating film 14 made of a silicon oxide film deposited on asemiconductor substrate 10.

[0016] As shown in FIG. 23(b), the interlayer insulating film 14 issubjected to anisotropic dry etching with an etching gas containingfluorine and carbon using the resist pattern 15 as a mask, to form acontact hole 16 to reach partway in the interlayer insulating film 14.

[0017] Isotropic dry etching is then performed for the interlayerinsulating film 14 with an etching gas including oxygen gas. By thisetching, as shown in FIG. 23(c), an opening 15 a of the resist pattern15 is widened, and with this, the diameter of the contact hole 16 ismade larger near the opening thereof, to provide a tapered wall at theopening of the contact hole 16.

[0018] As shown in FIG. 23(d), the resist pattern 15 is removed.Although illustration is omitted, by depositing a conductive material onthe interlayer insulating film 14, the contact hole 16 is filled withthe conductive material with reliability.

[0019] (First Problem)

[0020] The plasma etching for forming fine contact holes through anorganic/inorganic hybrid film is normally performed with an etching gascontaining fluorine and carbon, which can cleave Si—O bonds, as in theplasma etching of a silicon oxide film.

[0021] However, when the organic/inorganic hybrid film is etched withthe same etching gas under the same conditions as those used for etchingof the silicon oxide film, the etching rate largely decreases, or in anextreme case, the etching itself stops. The decrease in etching ratecauses reduction in throughput. This also causes reduction in thedifference between the etching rate of the interlayer insulating filmand that of the resist pattern, failing to secure a sufficiently largeetching selection ratio.

[0022] By adding oxygen gas to the etching gas, the etching rate of theorganic/inorganic hybrid film increases. However, this also facilitatesetching of the resist pattern 15, and thus the etching selection ratioof the interlayer insulating film 14 to the resist pattern 15 decreases.

[0023] The addition of oxygen gas to the etching gas also increases theetching rate of the silicon nitride film constituting the etchingstopper film 13. This reduces the etching selection ratio of theinterlayer insulating film 14 to the etching stopper film 13.

[0024] Therefore, it is not preferable to add oxygen gas to the etchinggas.

[0025] In view of the above, the first object of the present inventionis providing good plasma etching for an organic/inorganic hybrid film.

[0026] (Second Problem)

[0027] As described above, the etching stopper film 13 made of a siliconnitride film is deposited on the lower interconnection 12 made of acopper film, for example. The specific dielectric constant of thesilicon nitride film is about 7, which is significantly large comparedwith the specific dielectric constant of the organic/inorganic hybridfilm.

[0028] Having such an etching stopper film, therefore, the reduction inspecific dielectric constant between the upper and lowerinterconnections is not sufficiently attained despite of the formationof the interlayer insulating film 14 made of the organic/inorganichybrid film in an attempt to reduce the specific dielectric constant.

[0029] In view of the above, the second object of the present inventionis reducing the specific dielectric constant between the upper and lowerinterconnections by reducing the specific dielectric constant of theetching stopper film.

[0030] (Third Problem)

[0031] The second conventional example described above is an etchingtechnique in which the resist film is etched more isotropically to widenthe openings of the resist film by adding oxygen gas to the etching gas,to thereby provide contact holes having a tapered opening. However, thistechnique requires a large amount of etching of the resist film, andtherefore it is not possible to increase the thickness of the resistfilm in an attempt to form contact holes having a large aspect ratio.For this reason, the second conventional example finds difficulty inapplication to formation of contact holes having a large aspect ratio.In particular, in the case of forming tapered contact holes through theinterlayer insulating film made of an organic/inorganic hybrid film, howthe etching amount of the resist film should be reduced is a big problemto be solved.

[0032] There is also reported a technique in which the contact holes areetched into a tapered shape using an etching gas containing fluorine andcarbon without changing the diameter of the openings of the resist film.However, whether or not this technique is applicable to the formation ofcontact holes through the interlayer insulating film made of anorganic/inorganic hybrid film has not been verified.

[0033] In view of the above, the third object of the present inventionis providing a method in which contact holes having an increaseddiameter near the opening thereof can be formed through an interlayerinsulating film made of an organic/inorganic hybrid film withreliability.

[0034] (Fourth Problem)

[0035] In recent years, in order to enhance the resolution between lightexposed portions and non-exposed portions of a resist film, there hasbeen proposed a technique of forming a resist pattern using a chemicalamplification resist material. According to this technique, the polarity(solubility to a developer) is changed in portions of the resist filmmade of a chemical amplification resist material exposed to an energybeam by the function of acid generated in the exposed portions. Theexposed portions or non-exposed portions are then removed with thedeveloper, to form a resist pattern.

[0036] The present inventors formed a resist film by applying a chemicalamplification resist material to an organic/inorganic hybrid film, andsubjected the resist film to pattern light exposure. As a result, it wasfound that exposed portions of the resist film failed to sufficientlychange the polarity presumably due to a reduced amount of acid generatedin the exposed portions. Therefore, the resultant resist pattern afterremoval of the exposed portions or non-exposed portions of the resistfilm with a developer was faulty in shape.

[0037] The present inventors attempted to increase the exposure amountduring the pattern light exposure, but failed to sufficiently change thepolarity of the exposed portions of the resist film.

[0038] The faulty formation of the resist pattern did not occur when achemical amplification resist film was formed on a silicon oxide film,but was unique to the chemical amplification resist film formed on anorganic/inorganic hybrid film. The faulty formation of the resistpattern was confirmed to occur when using a positive chemicalamplification resist film, but is presumed to also occur when using anegative chemical amplification resist film.

[0039] Hereinafter, a problem occurring in the formation of multilayerinterconnections having a dual damascene structure, which uses achemical amplification resist pattern formed on an organic/inorganichybrid film, will be described with reference to FIGS. 24(a), 24(b), and25.

[0040] First, as shown in FIG. 24(a), a lower interconnection 22 isformed on an insulating film 21 deposited on a semiconductor substrate20. An etching stopper film 23 is deposited on the lower interconnection22, and then an interlayer insulating film 24 made of anorganic/inorganic hybrid film is deposited on the etching stopper film23. Thereafter, a contact hole 25 is formed through the interlayerinsulating film 24 by plasma etching using a first resist pattern thatis formed on the interlayer insulating film 24 and has an opening forformation of the contact hole.

[0041] A chemical amplification resist material is then applied to theresultant interlayer insulating film 24 to form a resist film. Theresist film is then subjected to pattern light exposure and development,to form a second resist pattern 26 having an opening for formation of aninterconnection resist pattern using a chemical amplification resistmaterial. According to this technique, the polarity (solubility to adeveloper) is changed in portions of the resist film made of a chemicalamplification resist material exposed to an energy beam by the functionof acid generated in the exposed portions. The exposed portions ornon-exposed portions are then removed with the developer, to form aresist pattern.

[0042] The present inventors formed a resist film by applying a chemicalamplification resist material to an organic/inorganic hybrid film, andsubjected the resist film to pattern light exposure. As a result, it wasfound that exposed portions of the resist film failed to sufficientlychange the polarity presumably due to a reduced amount of acid generatedin the exposed portions. Therefore, the resultant resist pattern afterremoval of the exposed portions or non-exposed portions of the resistfilm with a developer was faulty in shape.

[0043] The present inventors attempted to increase the exposure amountduring the pattern light exposure, but failed to sufficiently change thepolarity of the exposed portions of the resist film.

[0044] The faulty formation of the resist pattern did not occur when achemical amplification resist film was formed on a silicon oxide film,but was unique to the chemical amplification resist film formed on anorganic/inorganic hybrid film. The faulty formation of the resistpattern was confirmed to occur when using a positive chemicalamplification resist film, but is presumed to also occur when using anegative chemical amplification resist film.

[0045] Hereinafter, a problem occurring in the formation of multilayerinterconnections having a dual damascene structure, which uses achemical amplification resist pattern formed on an organic/inorganichybrid film, will be described with reference to FIGS. 24(a), 24(b), and25.

[0046] First, as shown in FIG. 24(a), a lower interconnection 22 isformed on an insulating film 21 deposited on a semiconductor substrate20. An etching stopper film 23 is deposited on the lower interconnection22, and then an interlayer insulating film 24 made of anorganic/inorganic hybrid film is deposited on the etching stopper film23. Thereafter, a contact hole 25 is formed through the interlayerinsulating film 24 by plasma etching using a first resist pattern thatis formed on the interlayer insulating film 24 and has an opening forformation of the contact hole.

[0047] A chemical amplification resist material is then applied to theresultant interlayer insulating film 24 to form a resist film. Theresist film is then subjected to pattern light exposure and development,to form a second resist pattern 26 having an opening for formation of aninterconnection groove. At this stage, the resist film partly remainsafter the above processing, forming a resist film 26 a over the topsurface of the interlayer insulating film 24 as well as the wall and thebottom of the contact hole 25. The reason why the resist film 26 a isformed is considered that acid has been reacted with some reactive groupand consumed.

[0048] Thereafter, the interlayer insulating film 24 is subjected toplasma etching using the second resist pattern 26 as a mask, to form aninterconnection groove 27 in the interlayer insulating film 24 as shownin FIG. 24(b). During this etching, a barrier (inner crown) 28 made ofthe interlayer insulating film 24 is formed since the resist film 26 aon the inner side of the interconnection groove 27 serves as a mask.

[0049] After removal of the second resist pattern 26 and the resist film26 a as shown in FIG. 25, the contact hole 25 and the interconnectiongroove 27 are filled with a conductive material to form a plug and anupper interconnection. At this time, due to the existence of the barrier28 on the inner side of the interconnection groove 27, the contactresistance between the upper interconnection embedded in theinterconnection groove 27 and the plug embedded in the contact hole 25disadvantageously increases.

[0050] In view of the above, the fourth object of the present inventionis preventing deactivation of acid in a chemical amplification resistfilm formed on an organic/inorganic hybrid film, to improve theresolution of the resist film.

SUMMARY OF THE INVENTION

[0051] (First Resolution Principle)

[0052] In order to solve the first problem, the present inventorsexamined the reason for the reduction of the etching rate when anorganic/inorganic hybrid film is subjected to plasma etching with anetching gas containing fluorine and carbon, and found the following.

[0053]FIG. 26(a) illustrates a cross-sectional structure of a contacthole 16 formed by dry-etching an interlayer insulating film 14A made ofa silicon oxide film with an etching gas containing fluorine and carbon.FIG. 26(b) illustrates a cross-sectional structure of a contact hole 16formed by dry-etching an interlayer insulating film 14B made of anorganic/inorganic hybrid film with an etching gas containing fluorineand carbon.

[0054] An etching gas normally contains a carbon component forprotection of the resist pattern 15. Therefore, in the dry etching ofthe interlayer insulating film 14A made of a silicon oxide film, a thinpolymer film 17A is deposited on a wall 16 a and a bottom 16 b of thecontact hole 16 as shown in FIG. 26(a). In this process, therefore, boththe deposition of the polymer film 17A and the etching proceed competingwith each other at the wall 16 a and the bottom 16 b of the contact hole16. At the bottom 16 b, however, the etching predominates over thedeposition. Accordingly, the bottom 16 b of the contact hole 16 movesdownward, that is, toward the etching stopper film 13.

[0055] In the case of dry etching of the interlayer insulating film 14Bmade of an organic/inorganic hybrid film, a carbon component iscontained, not only in the etching gas, but also in theorganic/inorganic hybrid film. Therefore, as shown in FIG. 26(b), anetching reaction gas containing a carbon component is generated at thewall 16 a and the bottom 16 b of the contact hole 16 during the etchingof the organic/inorganic hybrid film. As a result, a polymer film 17Bhaving a larger thickness than that shown in FIG. 26(a) is deposited. Inthis case, also, both the deposition of the polymer film 17B and theetching proceed competing with each other at the bottom 16 b of thecontact hole 16. However, in this case, progress of the etching isblocked by the carbon component at the bottom 16 b as the etchingsurface of the organic/inorganic hybrid film, together with the polymerfilm 17B. In the early stage of the etching, that is, when the depth ofthe contact hole 16 is small, when the introduced amount of the plasmaetching species and the plasma energy are sufficient, the etchingpredominates over the deposition of the polymer film 17B, and thereforethe etching proceeds. As the contact hole 16 becomes deeper with theprogress of the etching, however, the introduced amount of the plasmaetching species and the plasma energy become insufficient, failing tosufficiently remove the carbon component in the organic/inorganic hybridfilm. Therefore, a surplus of the carbon component is accumulated on thebottom 16 b of the contact hole 16, blocking smooth etching reaction.Since the deposition of the polymer film 17B predominates over theetching, the etching rate gradually decreases, and finally the etchingstops.

[0056] In consideration of the above, if the etching is carried outwhile sufficiently removing the polymer film on the bottom of thecontact hole and the carbon component existing in the portion of theorganic/inorganic hybrid film exposed in the contact hole, the etchingshould proceed smoothly.

[0057] The first and second etching methods according to the presentinvention are based on the first resolution principle described above.

[0058] The first etching method of the present invention is directed toa method for plasma-etching an organic/inorganic hybrid film representedby SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0), including the step of:plasma-etching the organic/inorganic hybrid film while eliminating acarbon component from a surface portion of the organic/inorganic hybridfilm.

[0059] According to the first etching method, the plasma etching isperformed while the surface portion of the organic/inorganic hybrid filmis reformed by elimination of a carbon component from the surfaceportion of the organic/inorganic hybrid film. Therefore, in thecarbon-eliminated surface portion, in which the amount of the carboncomponent that facilitates deposition of a polymer film is small, theetching rate improves.

[0060] The second etching method of the present invention is directed toa method for plasma-etching an organic/inorganic hybrid film representedby SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0), including repeating alternately afirst step of eliminating a carbon component from a surface portion ofthe organic/inorganic hybrid film and a second step of plasma-etchingthe surface portion from which the carbon component has been eliminated.

[0061] According to the second etching method, the first step ofeliminating a carbon component from the surface portion of theorganic/inorganic hybrid film and the second step of plasma-etching thesurface portion from which the carbon component has been eliminated areperformed alternately. Therefore, in the carbon-eliminated surfaceportion, in which the amount of the carbon component that facilitatesdeposition of a polymer film is small, the etching rate improves.

[0062] In the first or second etching method, plasma etching isperformed in the state where the carbon component has been eliminatedfrom the surface portion of the organic/inorganic hybrid film, that is,in the state where the amount of the carbon component that blockscleaving of Si—O bonds and generation of CO₂, SiF₄, and the like issmall in the surface portion of the organic/inorganic hybrid film.Therefore, the etching rate improves. This improves the throughput andalso increases the etching selection ratio with respect to the resistpattern.

[0063] The second etching method is especially effective in the casethat the preferred conditions under which the carbon component iseliminated from the surface portion are different from the preferredconditions under which the surface portion is plasma-etched, such as thecase that the preferred gas pressure adopted when the carbon componentis eliminated from the surface portion is largely different from thepreferred gas pressure adopted when the organic/inorganic hybrid film isplasma-etched.

[0064] In the first etching method, the plasma etching is preferablyperformed with an etching gas containing fluorine, carbon and nitrogen.

[0065] In the second etching method, preferably, the first step isperformed with a gas containing nitrogen, and the second step isperformed with an etching gas containing fluorine and carbon.

[0066] In the above case, the gas containing nitrogen may be a mixed gasof hydrogen and nitrogen or ammonia gas.

[0067] When a gas containing nitrogen comes into contact with thesurface of an organic/inorganic hybrid film represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0), “C_(x)H_(y)” is chemically changed tohighly volatile HCN or CN at the surface of the SiC_(x)H_(y)O_(z) film,and thus the proportion of the carbon component decreases in the surfaceportion of the organic/inorganic hybrid film (SiC_(x)H_(y)O_(z) film).Therefore, the etching of the organic/inorganic hybrid film proceeds atroughly the same etching rate as that for a silicon oxide film. Thismechanism will be described according to reaction formulae as follows.

[0068] When a gas containing nitrogen comes into contact with thesurface of the organic/inorganic hybrid film represented bySiC_(x)H_(y)O_(z), chemical reaction represented by Formula 1 or Formula2 below proceeds.

[0069] That is, in the surface portion of the organic/inorganic hybridfilm, the carbon component is eliminated, to provide a reformed filmhaving a composition similar to that of a silicon oxide film.

[0070] Thereafter, when an etching gas containing fluorine and carboncomes into contact with the reformed layer of the organic/inorganichybrid film, the CF_(x) contained in the etching gas reacts with thereformed layer as represented by Formula 3 or Formula 4 below, and thusetching proceeds.

[0071] Thus, “C_(x)H_(y)” is removed from the surface portion of theSiC_(x)H_(y)O_(z) film, to form the reformed layer represented bySiH_(y-x)O_(z) or SiH_(y)O_(z), and the reformed layer is then etchedwith an etching gas containing fluorine and carbon. In this way, theplasma etching can be performed for the organic/inorganic hybrid film(SiC_(x)H_(y)O_(z) film) at roughly the same etching rate as that for asilicon oxide film (SiO₂ film).

[0072] The above phenomenon that C or C_(x)H_(y) is removed from theSiC_(x)H_(y)O_(z) film implies that the proportion of oxygen atoms inthe film increases. This phenomenon can therefore be considered asoxidation.

[0073] The reformation of the surface portion of the SiC_(x)H_(y)O_(z)film is a process of removing the carbon component in the surfaceportion of the SiC_(x)H_(y)O_(z) film by changing the carbon componentto HCN or CN. Therefore, if no hydrogen atoms or only a small amount ofhydrogen atoms are contained in the SiC_(x)H_(y)O_(z) film, hydrogen gasmay be mixed in the gas for reformation to enable efficient progress ofthe reformation and thus the etching.

[0074] In plasma etching of an inorganic insulating film containing nocarbon component at all, such as a SiOF film, there is known an etchingmethod using an etching gas obtained by mixing a nitride such as NH₃ ina CF₄ gas that is normally used for etching of a silicon oxide film(Japanese Laid-Open Patent Publication No. 9-263050).

[0075] The above conventional etching method is based on a technicalthought as follows. By mixing a nitride in the etching gas, fluorineradicals (F*) in the plasma of the etching gas are scavenged by hydrogenatoms (H), nitrogen atoms (N), or active species thereof freely existingin the plasma, to thereby enhance the selectivity with respect to asilicon substrate or a resist film. This technical thought in JapaneseLaid-Open Patent Publication No. 9-263050 is therefore completelydifferent from the etching method of the present invention in which agas containing a nitrogen component is used for eliminating a carboncomponent from the surface portion of an organic/inorganic hybrid filmrepresented by SiC_(x)H_(y)O_(z.)

[0076] (Second Resolution Principle)

[0077] The second resolution principle is for solving the second problemdescribed above. This utilizes the mechanism that the etching rate isreduced by the existence of a carbon component contained in anorganic/inorganic hybrid film represented by SiC_(x)H_(y)O_(z). That is,an organic/inorganic hybrid film is used as the etching stopper film, inplace of a silicon nitride film conventionally used. More specifically,under the interlayer insulating film made of an organic/inorganic hybridfilm, an etching stopper film made of an organic/inorganic hybrid filmin which the proportion of the carbon component is large compared withthe interlayer insulating film is provided.

[0078] In place of the organic/inorganic hybrid film, any of siliconinsulating films in which the proportion of the carbon component islarge, such as a SiC film and the like, may be used.

[0079] The first fabricating method for a semiconductor device of thepresent invention includes the steps of: depositing an etching stopperfilm on an interconnection layer formed on a substrate, the etchingstopper film being represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) inwhich the proportion of carbon atoms with respect to silicon atoms isrelatively large; depositing an interlayer insulating film on theetching stopper film, the interlayer insulating film being representedby SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportion of carbonatoms with respect to silicon atoms is relatively small; and forming acontact hole through the interlayer insulating film by plasma-etchingthe interlayer insulating film.

[0080] The first semiconductor device of the present invention includes:an etching stopper film formed on an interconnection layer formed on asubstrate, the etching stopper film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) in which the proportion of carbonatoms with respect to silicon atoms is relatively large; an interlayerinsulating film formed on the etching stopper film, the interlayerinsulating film being represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0)in which the proportion of carbon atoms with respect to silicon atoms isrelatively small; and a contact hole formed through the interlayerinsulating film by plasma etching.

[0081] According to the first fabricating method of a semiconductordevice and the first semiconductor device, the etching stopper filmcontaining a carbon component in a large proportion compared with theinterlayer insulating film is formed under the interlayer insulatingfilm. Therefore, once the plasma etching of the interlayer insulatingfilm is completed, the following phenomenon occurs. The etching stopperfilm containing a larger amount of a carbon component is more or lessetched and generates an etching reaction gas containing a carboncomponent, which is mixed in the plasma. In addition, a large amount ofthe carbon component exists in the etching stopper film and on thesurface thereof. Therefore, a thick polymer film is deposited on thebottom of the contact holes and this sharply reduces the etching rate ofthe etching stopper film.

[0082] Thus, the etching stopper film made of the secondorganic/inorganic hybrid film in which the proportion of the carboncomponent is relatively large serves as the etching stopper film for theinterlayer insulating film made of the first organic/inorganic hybridfilm in which the proportion of the carbon component is relatively smallwhen the latter is plasma-etched to form a contact hole.

[0083] In addition, since the above etching stopper film is made of aninsulating film having a low specific dielectric constant, the specificdielectric constant between the lower and upper interconnections can belargely reduced, compared with the case of using a silicon nitride filmhaving a large specific dielectric constant.

[0084] In the first fabricating method of a semiconductor device, theplasma etching is performed with an etching gas containing fluorine,carbon and nitrogen.

[0085] (Third Resolution Principle)

[0086] The third resolution principle is for solving the third problemdescribed above. This utilizes the mechanism that the etching rate isreduced by the existence of a carbon component contained in anorganic/inorganic hybrid film represented by SiC_(x)H_(y)O_(z).Specifically, the mechanism is that with increase in the amount of thecarbon component contained in an organic/inorganic hybrid film, thepolymer film deposited on the wall of a contact hole is thicker and thisreduces the etching rate, and with decrease in the amount of the carboncomponent contained in the organic/inorganic hybrid film, the polymerfilm deposited on the wall of the contact hole is thinner and thisincreases the etching rate. The third resolution principle can berealized by the following first and second schemes.

[0087] In the first scheme, the lower part of the interlayer insulatingfilm is made of a first organic/inorganic hybrid film that contains acarbon component in a relatively small proportion, and the upper part ofthe interlayer insulating film is made of a second organic/inorganichybrid film that contains a carbon component in a relatively largeproportion. Plasma etching is carried out for the upper and lower partsof the interlayer insulating film under the same conditions.

[0088] In the second scheme, a fixed proportion of a carbon component iscontained in the interlayer insulating film made of an organic/inorganichybrid film. In the early stage of plasma etching of the interlayerinsulating film (etching of the upper part of the interlayer insulatingfilm), the amount of the carbon component eliminated from the wall andthe bottom of the contact hole is kept relatively small, while in thelate stage of the plasma etching of the interlayer insulating film(etching of the lower part of the interlayer insulating film), theamount of the carbon component eliminated from the wall and the bottomof the contact hole is made relatively large.

[0089] The second fabricating method for a semiconductor device of thepresent invention, which embodies the first scheme of the thirdresolution principle, includes the steps of: depositing a firstinterlayer insulating film on an interconnection layer formed on asubstrate, the first interlayer insulating film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) in which the proportion of carbonatoms with respect to silicon atoms is relatively small; depositing asecond interlayer insulating film on the first interlayer insulatingfilm, the second interlayer insulating film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportion of carbonatoms with respect to silicon atoms is relatively large; andplasma-etching the second interlayer insulating film and the firstinterlayer insulating film sequentially, to form a first opening throughthe second interlayer insulating film, the diameter of the first openingbeing smaller toward the bottom end, and a second opening through thefirst interlayer insulating film, the wall of the second opening beingvertical to the bottom surface.

[0090] The second semiconductor device of the present inventionincludes: a first interlayer insulating film deposited on a substrate,the first interlayer insulating film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) in which the proportion of carbonatoms with respect to silicon atoms is relatively small; a secondinterlayer insulating film deposited on the first interlayer insulatingfilm, the second interlayer insulating film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportion of carbonatoms with respect to silicon atoms is relatively large; a first openingformed through the second interlayer insulating film by plasma-etching,the diameter of the first opening being smaller toward the bottom end;and a second opening formed under the first opening through the firstinterlayer insulating film, the wall of the second opening beingvertical to the bottom surface.

[0091] According to the second fabricating method for a semiconductordevice and the second semiconductor device, the second interlayerinsulating film deposited on the first interlayer insulating filmcontains a larger proportion of the carbon component than the firstinterlayer insulating film. Therefore, the following phenomenon occursduring the plasma etching of the second interlayer insulating film. Boththe deposition of a polymer film and the etching proceeds competing witheach other at the bottom of the first opening. In this occasion,however, an etching reaction gas containing a large amount of the carboncomponent is generated during the etching of the second interlayerinsulating film, which facilitates deposition of polymer on the wall andthe bottom of the first opening. In addition, the carbon component inthe second interlayer insulating film blocks progress of the etching atthe bottom, causing reduction in etching rate toward the bottom.Therefore, with the progress of the etching toward the bottom of thefirst opening, a larger amount of polymer is deposited on the wall ofthe first opening. As a result, formed is the first opening of which thediameter is smaller toward the bottom.

[0092] The first interlayer insulating film contains a smallerproportion of the carbon component than the second interlayer insulatingfilm. Therefore, the following phenomenon occurs during plasma etchingof the first interlayer insulating film. Both the deposition of apolymer film and the etching proceeds competing with each other at thebottom of the second opening. In this occasion, only a comparativelysmall amount of an etching reaction gas is generated from the firstinterlayer insulating film during the etching thereof, and thusdeposition of a polymer film on the wall and the bottom of the secondopening is small. This enables a sufficient amount of the carboncomponent to be eliminated from the first interlayer insulating film atthe bottom of the second opening, and thus prevents reduction in etchingrate toward the bottom. Therefore, with the progress of the etchingtoward the bottom of the second opening, only a small amount of polymeris deposited on the wall of the second opening. As a result, formed isthe second opening of which the wall is roughly vertical to the bottomface.

[0093] In the second fabricating method of a semiconductor device, theplasma etching is preferably performed with an etching gas containingfluorine, carbon and nitrogen.

[0094] The third fabricating method for a semiconductor device of thepresent invention, which embodies the second scheme of the thirdresolution principle, includes the steps of: depositing an interlayerinsulating film represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) on asubstrate; performing first plasma-etching for the interlayer insulatingfilm while blocking or suppressing a carbon component from beingeliminated from a surface portion of the interlayer insulating film, toform a first opening in the interlayer insulating film, the diameter ofthe first opening being smaller toward the bottom end; and performingsecond plasma etching for the interlayer insulating film whilefacilitating elimination of the carbon component from the surfaceportion of the interlayer insulating film, to form a second openingunder the first opening in the interlayer insulating film, the wall ofthe first opening being vertical to the bottom surface.

[0095] According to the third fabricating method for a semiconductordevice, in the first plasma etching for the interlayer insulating film,which is performed while blocking or suppressing the carbon componentfrom being eliminated from the surface portion of the interlayerinsulating film, the following phenomenon occurs. Both the deposition ofa polymer film and the etching proceeds competing with each other at thebottom of the first opening. In this occasion, however, sinceelimination of the carbon component from the interlayer insulating filmis blocked or reduced, progress of the etching is impeded, and thus theetching rate decreases toward the bottom. Therefore, with the progressof the etching toward the bottom, a larger amount of polymer isdeposited on the wall. As a result, the first opening of which thediameter is smaller toward the bottom is formed in the upper part of theinterlayer insulating film.

[0096] In the second plasma etching for the interlayer insulating film,which is performed while facilitating elimination of the carboncomponent from the surface portion of the interlayer insulating film,the following phenomenon occurs. Both the deposition of a polymer filmand the etching proceeds competing with each other at the bottom of thesecond opening. In this occasion, since the carbon component issufficiently eliminated from the surface of the interlayer insulatingfilm, the etching rate does not decrease with progress of the etchingtoward the bottom. Therefore, only a small amount of polymer isdeposited on the wall in comparison with the progress of the etchingtoward the bottom. As a result, the second opening of which the wall isvertical to the bottom face is formed in the lower part of theinterlayer insulating film.

[0097] In the third fabricating method for a semiconductor device,preferably, the first plasma etching is performed with a first etchinggas containing fluorine, carbon and nitrogen in which the proportion ofnitrogen is relatively small, and the second plasma etching is performedwith a second etching gas containing fluorine, carbon and nitrogen inwhich the proportion of nitrogen is relatively large.

[0098] (Fourth Resolution Principle)

[0099] As described above, the phenomenon that acid generated in theexposed portions of the resist film is deactivated is unique to thechemical amplification resist film formed on an organic/inorganic hybridfilm, and does not occur in the chemical amplification resist filmformed on a silicon oxide film. It is not possible to prevent this aciddeactivation by increasing the exposure of an energy beam emitted to theresist film. From these facts and others, the acid deactivation ispresumed to occur as a result of reaction of acid (H⁺) generated in theexposed portions with a reactive group contained in theorganic/inorganic hybrid film.

[0100] In the fourth resolution principle, therefore, a silicon oxidefilm is interposed between the organic/inorganic hybrid film and thechemical amplification resist film for blocking the reaction of acidgenerated in the exposed portions with a reactive group contained in theorganic/inorganic hybrid film.

[0101] The fourth fabricating method for a semiconductor device of thepresent invention includes the steps of: depositing an interlayerinsulating film represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) on asubstrate; forming a silicon oxide film containing no carbon componenton the top surface or a surface portion of the interlayer insulatingfilm; forming a resist film made of a chemical amplification resistmaterial on the silicon oxide film; and subjecting the resist film topattern exposure and development to form a resist pattern made of theresist film.

[0102] According to the fourth fabricating method for a semiconductordevice, the silicon oxide film containing no reaction group existsbetween the interlayer insulating film and the resist film made of thechemical amplification resist material. Therefore, acid generated inexposed portions of the resist film is prevented from reacting with thecarbon component contained in the interlayer insulating film, and thusprevented from deactivation. This ensures the polarity (solubility to adeveloper) of the exposed portions of the resist film, and thus afterremoval of the exposed portions or non-exposed portions of the resistfilm with a developer, the resultant resist pattern is good in shape.

[0103] In the fourth fabricating method for a semiconductor device, thesilicon oxide film may be formed by eliminating a carbon component fromthe surface portion of the interlayer insulating film.

[0104] The fifth fabricating method for a semiconductor device of thepresent invention includes the steps of: depositing an etching stopperfilm on an interconnection layer formed on a substrate, and thendepositing an interlayer insulating film represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) on the etching stopper film; forming acontact hole through the interlayer insulating film; forming a resistpattern made of a chemical amplification resist material, the resistpattern having an opening for formation of an interconnection groove,and also forming a protection film made of the chemical amplificationresist material on the bottom of the contact hole for protecting theetching stopper film; and plasma-etching the interlayer insulating filmusing the resist pattern, to form the interconnection groove in theinterlayer insulating film.

[0105] According to the fifth fabricating method for a semiconductordevice, the protection film made of a chemical amplification resistmaterial is formed on the bottom of the contact hole for protecting theetching stopper film. With the protection film formed in the contacthole, the interlayer insulating film is plasma-etched to form aninterconnection groove therein. Therefore, the portion of the etchingstopper film exposed in the contact hole is prevented from being exposedto the plasma for formation of the interconnection groove and thus isdamaged less easily. Using this method, the etching stopper film can bemade thin and still can protect the interconnection layer from beingstill can protect the interconnection layer from being exposed to theplasma. It is therefore possible to avoid damaging of the surface of theinterconnection layer or formation of a naturally oxidized film on thesurface of the interconnection layer.

[0106] The sixth fabricating method for a semiconductor device of thepresent invention, which corresponds to application of the first andsecond resolution principles to a fabrication process of a semiconductordevice, includes the steps of: depositing an etching stopper film on aninterconnection layer formed on a substrate, the etching stopper filmbeing represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) in which theproportion of carbon atoms with respect to silicon atoms is relativelylarge; depositing an interlayer insulating film on the etching stopperfilm, the interlayer insulating film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportion of carbonatoms with respect to silicon atoms is relatively small; depositing aCMP stopper film on the interlayer insulating film; forming a resistpattern having an opening for formation of a contact hole on the CMPstopper film; transferring the opening of the resist pattern to the CMPstopper film, and then plasma-etching the interlayer insulating filmwhile eliminating a carbon component from a surface portion of theinterlayer insulating film, to form a contact hole through theinterlayer insulating film; after removal of the resist pattern,depositing a conductive film resist pattern, depositing a conductivefilm on the CMP stopper film to fill the contact hole with theconductive film; and removing a portion of the conductive film exposedon the CMP stopper film by CMP, to form a plug made of the conductivefilm.

[0107] According to the sixth fabricating method for a semiconductordevice, a contact hole is formed through the interlayer insulating filmby performing plasma etching while eliminating the carbon component fromthe surface portion of the interlayer insulating film. Formation of apolymer film is reduced on the surface portion from which the carboncomponent has been eliminated. Therefore, the etching rate does notdecrease, and thus the contact hole can be formed through the interlayerinsulating film with reliability.

[0108] The etching stopper film containing a carbon component in a largeproportion compared with the interlayer insulating film is formed underthe interlayer insulating film. Therefore, once the plasma etching ofthe interlayer insulating film is completed, the following phenomenonoccurs. The etching stopper film containing a larger amount of a carboncomponent is more or less etched and generates an etching reaction gascontaining a carbon component, which is mixed in the plasma. Inaddition, a large amount of the carbon component exists in the etchingstopper film and on the surface thereof. Therefore, a thick polymer filmis deposited on the bottom of the contact hole, and this sharply reducesthe etching rate of the etching stopper film. Thus, the etching stopperfilm in which the proportion of the carbon component is relatively largeserves as the etching stopper film when the interlayer insulating filmis plasma-etched to form a contact hole.

[0109] In addition, the etching stopper film is made of an insulatingfilm having a low specific dielectric constant, and thus enables largereduction in the specific dielectric constant between the lower andupper interconnections, compared with a silicon nitride film having alarge specific dielectric constant.

[0110] Moreover, the CMP stopper film is interposed between theinterlayer insulating film and the conductive film for formation of theplug. The interlayer insulating film is therefore protected from beingsubjected to CMP when the portion of the conductive film exposed on theCMP stopper film is removed by CMP. Therefore, the interlayer insulatingfilm is prevented from being damaged even though it is made of anorganic/inorganic hybrid film that is susceptible to CMP.

[0111] The seventh fabricating method for a semiconductor device of thepresent invention, which corresponds to application of the first andsecond resolution principles to a fabrication process of multilayerinterconnections having a dual damascene structure, includes the stepsof: depositing an etching stopper film on a lower interconnection formedon a substrate, the etching stopper film being represented bySiC_(x)H_(y)O_(z) (x>0, y>0, z>0) in which the proportion of carbonatoms with respect to silicon atoms is relatively large; depositing aninterlayer insulating film on the etching stopper film, the interlayerinsulating film being represented by SiC_(x)H_(y)O_(z) (x>0, y>0, z>0)in which the proportion of carbon atoms with respect to silicon atoms isrelatively small; depositing a CMP stopper film on the interlayerinsulating film; forming a first resist pattern having an opening forformation of a contact hole on the CMP stopper film; transferring theopening of the first resist pattern to the CMP stopper film, and thenplasma-etching the interlayer insulating film while eliminating a carboncomponent from a surface portion of the second organic/inorganic hybridfilm, to form a contact hole through the interlayer insulating film;after removal of the first resist pattern, forming a second resistpattern having an opening for formation of an interconnection groove onthe CMP stopper film; transferring the opening of the second resistpattern to the CMP stopper film, and then plasma-etching the interlayerinsulating film while eliminating a carbon component from a surfaceportion of the interlayer insulating film, to form an interconnectiongroove in the interlayer insulating film; depositing a conductive filmon the CMP stopper film to fill the contact hole and the interconnectiongroove with the conductive film; and removing a portion of theconductive film exposed on the CMP stopper film by CMP, to form a plugand an upper interconnection made of the conductive film.

[0112] According to the seventh fabricating method for a semiconductordevice, as in the sixth fabricating method, a contact hole is formedthrough the interlayer insulating film by performing plasma etchingwhile eliminating the carbon component from the surface portion of theinterlayer insulating film. Therefore, the etching rate does notdecrease, and thus the contact hole and the interconnection groove canbe formed in the interlayer insulating film with reliability.

[0113] The etching stopper film in which the proportion of the carboncomponent is relatively large compared with the interlayer insulatingfilm serves as the etching stopper film when the interlayer insulatingfilm is plasma-etched to form a contact hole and an interconnectiongroove.

[0114] In addition, the etching stopper film is made of an insulatingfilm having a low specific dielectric constant, and thus enables largereduction in the specific dielectric constant between the lower andupper interconnection, compared with a silicon nitride film having alarge specific dielectric constant.

[0115] Moreover, the CMP stopper film is interposed between theinterlayer insulating film and the conductive film for formation of theplug and the upper interconnection. The interlayer insulating film istherefore protected from being subjected to CMP when the portion of theconductive film exposed on the CMP stopper film is removed by CMP.Therefore, the interlayer insulating film is prevented from beingdamaged even though it is made of an organic/inorganic hybrid film thatis susceptible to CMP.

[0116] Thus, it is ensured to reduce the specific dielectric constantbetween the lower and upper interconnections in multilayerinterconnections having a dual damascene structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0117]FIG. 1 is a cross-sectional view of the entire construction of aplasma processing apparatus used in embodiments of the presentinvention.

[0118]FIG. 2 is a flowchart of an etching method of the first embodimentof the present invention.

[0119]FIG. 3 is a cross-sectional view for description of a mechanism ofreforming and then etching a surface portion of an organic/inorganichybrid film in the etching method of the first embodiment of the presentinvention.

[0120]FIG. 4 is a view showing the timing at which a gas containing a N₂component and CF gas are fed in the first embodiment of the presentinvention.

[0121] FIGS. 5(a) and 5(b) are views showing the relationships betweenthe distance in the depth direction and the atomic concentrationobtained from XPS analysis of film types a and b, respectively, of theorganic/inorganic hybrid film.

[0122] FIGS. 6(a) and 6(b) are views showing the relationships betweenthe distance in the depth direction and the atomic concentrationobtained from XPS analysis of film types c and d, respectively, of theorganic/inorganic hybrid film.

[0123]FIG. 7 is a view showing the relationship between the distance inthe depth direction and the atomic concentration for a film obtained byreforming the film type c of the organic/inorganic hybrid film usingNH₃/N₂ gas.

[0124]FIG. 8 is a flowchart of an etching method of the secondembodiment of the present invention.

[0125]FIG. 9 is a view showing the timing at which a gas containing a N₂component and CF gas are fed in the second embodiment of the presentinvention.

[0126]FIG. 10(a) is a cross-sectional view illustrating a fabricatingmethod for a semiconductor device of the third embodiment of the presentinvention, and

[0127]FIG. 10(b) is a cross-sectional view illustrating a fabricatingmethod for a semiconductor device of a modification of the thirdembodiment of the present invention.

[0128] FIGS. 11(a) through 11(c) are cross-sectional views of processsteps of a fabricating method for a semiconductor device of the fourthembodiment of the present invention.

[0129] FIGS. 12(a) through 12(c) are cross-sectional views of processsteps of a fabricating method for a semiconductor device of the fifthembodiment of the present invention.

[0130]FIG. 13 is a view showing the timing at which a gas containing aN₂ component and CF gas are fed in the fifth embodiment of the presentinvention.

[0131] FIGS. 14(a) through 14(c) are cross-sectional views of processsteps of a fabricating method for a semiconductor device of the sixthembodiment of the present invention.

[0132] FIGS. 15(a) through 15(d) are cross-sectional views of processsteps of the fabricating method for a semiconductor device of the sixthembodiment of the present invention.

[0133] FIGS. 16(a) through 16(c) are cross-sectional views of processsteps of a fabricating method for a semiconductor device of the seventhembodiment of the present invention.

[0134] FIGS. 17(a) through 17(c) are cross-sectional views of processsteps of the fabricating method for a semiconductor device of theseventh embodiment of the present invention.

[0135] FIGS. 18(a) through 18(d) are cross-sectional views of processsteps of the fabricating method for a semiconductor device of theseventh embodiment of the present invention.

[0136] FIGS. 19(a) through 19(c) are cross-sectional views of processsteps of a fabricating method for a semiconductor device of the eighthembodiment of the present invention.

[0137] FIGS. 20(a) through 20(d) are cross-sectional views of processsteps of the fabricating method for a semiconductor device of the eighthembodiment of the present invention.

[0138] FIGS. 21(a) through 21(c) are cross-sectional views of processsteps of a fabricating method for a semiconductor device of the secondmodification of the eighth embodiment of the present invention.

[0139] FIGS. 22(a) through 22(d) are cross-sectional views of processsteps of the first conventional fabricating method for a semiconductordevice.

[0140] FIGS. 23(a) through 23(d) are cross-sectional views of processsteps of the second conventional fabricating method for a semiconductordevice.

[0141] FIGS. 24(a) and 24(b) are cross-sectional views for descriptionof a problem occurring when a chemical amplification resist film isformed on an interlayer insulating film made of an organic/inorganichybrid film.

[0142]FIG. 25 is a cross-sectional view for description of the problemoccurring when a chemical amplification resist film is formed on aninterlayer insulating film made of an organic/inorganic hybrid film.

[0143]FIG. 26(a) is a cross-sectional view of a contact hole formed bydry-etching an interlayer insulating film made of a silicon oxide filmwith an etching gas containing fluorine and carbon, and

[0144]FIG. 26(b) is a cross-sectional view of a contact hole formed bydry-etching an interlayer insulating film made of an organic/inorganichybrid film with an etching gas containing fluorine and carbon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0145] (Plasma Processing Apparatus)

[0146] Hereinafter, embodiments of the etching methods according to thepresent invention will be described. First, as a precondition for theembodiments, a plasma processing apparatus used for etching will bedescribed with reference to FIG. 1.

[0147]FIG. 1 shows a cross-sectional structure of the plasma processingapparatus. A lower electrode 11, which is used as a sample mount, isplaced in a lower portion of a reaction chamber 10 and holds asemiconductor substrate 12 by electrostatic adsorption. An upperelectrode 13 is placed in the upper portion of the reaction chamber 10to face the lower electrode 11. An etching gas is fed into the reactionchamber 10 via a gas inlet 14 formed at the upper electrode 13. The gasinside the reaction chamber 10 is discharged by a vacuum pump 15disposed under the reaction chamber 10.

[0148] A plasma induction coil 17 is placed on the reaction chamber 10with an insulator 16 therebetween. An end of the plasma induction coil17 is connected to a first high-frequency source 19 via a first matchingdevice 18, while the other end is grounded. The lower electrode 11 isconnected to a second high-frequency source 21 via a second matchingdevice 20.

[0149] When a first high-frequency power is applied to the plasmainduction coil 17 from the first high-frequency source 19, ahigh-frequency induced magnetic field is generated inside the reactionchamber 10, so that the etching gas fed in the reaction chamber 10becomes plasma. When a second high-frequency power is applied to thelower electrode 11 from the second high-frequency source 21, the plasmagenerated in the reaction chamber 10 is directed to the lower electrode11, that is, to the semiconductor substrate 12, which is thus exposed tothe plasma.

[0150] (First Embodiment)

[0151] A plasma etching method of the first embodiment of the presentinvention carried out using the plasma processing apparatus describedabove will be described with reference to FIGS. 1, 2, 3, 4, 5(a), 5(b),6(a), 6(b), and 7.

[0152] First, as shown in FIG. 3, an interconnection layer 102 made ofan aluminum film, a copper film, an alloy film of aluminum or copper asa main component, or the like is embedded in an insulating film 101deposited on a semiconductor substrate 100. Note that, althoughillustration is omitted in FIG. 3, the sides and the bottom of theinterconnection layer 102 are coated with barrier metal that preventsmetal atoms constituting the interconnection layer 102 from dispersinginto the insulating film 101.

[0153] Thereafter, an etching stopper film 103 is deposited on theentire top surface of the semiconductor substrate 100 including theinterconnection layer 102. The etching stopper film 103, which is madeof a silicon nitride film, for example, protects the interconnectionlayer 102 and also serves as an etching stopper. The etching stopperfilm 103 is especially required when a dual damascene interconnectionstructure is formed, and prevents, the interconnection layer 102 frombeing oxidized with an etching gas during etching of anorganic/inorganic hybrid film 104 described below. The etching stopperfilm 103 also prevents the etching apparatus from being polluted withmetal.

[0154] The organic/inorganic hybrid film 104 represented bySiC_(x)H_(y)O_(z) (>0, y>0, z>0) is then deposited on the etchingstopper film 103 using a known CVD apparatus. A resist pattern 105having openings for formation of contact holes is formed on theorganic/inorganic hybrid film 104.

[0155] As the gas for deposition of the organic/inorganic hybrid film104, usable is a mixed gas of a material gas such as tetramethylsilane(Si(CH₃)₄), dimethyl.dimethylsiloxane (Si(CH₃)₂(—O—CH₃)₂),monomethylsilane (SiH₃(CH₃)), or Hexamethyldisiloxane(Si(CH₃)₃—O—Si(CH₃)₃) and an additive gas such as N₂O. In the firstembodiment, a mixed gas of hexamethyldisiloxane (HMDSO) and N₂O was fedinto the CVD apparatus, to deposit the organic/inorganic hybrid film 104made of a hexamethyldisiloxane film on the semiconductor substrate 100that is kept at 300° C.

[0156] Thereafter, in step SA1 shown in FIG. 2, the resultantsemiconductor substrate 100 is placed in the reaction chamber 10 of theplasma etching apparatus shown in FIG. 1. In step SA2, the semiconductorsubstrate 100 is fixed to the lower electrode 11 by electrostaticadsorption.

[0157] In step SA3, an etching gas containing fluorine, carbon andnitrogen is fed into the reaction chamber 10 in a manner as shown inFIG. 4. An example of the etching gas containing fluorine, carbon andnitrogen is a mixed gas of a fluorocarbon (CF) gas normally used foretching of a SiO₂ film and a N₂ gas. Details of the etching gascontaining fluorine, carbon and nitrogen will be described later.

[0158] In step SA4, the first high-frequency power is applied to theplasma induction coil 17 from the first high-frequency source 19, togenerate plasma between the lower electrode 11 and the upper electrode13. Also, the second high-frequency power is applied to the lowerelectrode 11 from the second high-frequency source 21. With thisapplication, the etching species in the plasma are attracted to thesemiconductor substrate 100. As a result, in step SA5, theorganic/inorganic hybrid film 104 is plasma-etched using the resistpattern 105 as a mask.

[0159] Once the organic/inorganic hybrid film 104 has been etched to apredetermined depth, in step SA6, the application of the high-frequencyvoltages to the upper electrode 13 and the lower electrode 11 and thefeeding of the etching gas are stopped, to finish the etching.

[0160] Hereinafter, an example of the etching gas used for the plasmaetching of the organic/inorganic hybrid film 104, as well as the etchingconditions thereof, will be described.

[0161] First, an etching gas having a volume flow ratio of

[0162] C₄F₈:CH₂F₂:Ar:CO:N₂=2:1:10:5:0.5 is fed via the gas inlet 14 intothe reaction chamber 10 that is kept at a pressure of 2.6 Pa. The firsthigh-frequency power of 1500 W at 13.56 MHz, for example, is applied tothe plasma induction coil 17 from the first high-frequency source 19, togenerate plasma between the lower electrode 11 and the upper electrode13. Also, the second high-frequency power of 1400 W at 4 MHz, forexample, is applied to the lower electrode 11 from the secondhigh-frequency source 21, to attract the etching species in the plasmato the semiconductor substrate 100 to thereby enable plasma etching.

[0163] By the plasma etching described above, the etching species suchas N₂ contained in the plasma are attracted to the bottom of a contacthole 104 a, and reacts with carbon atoms and hydrogen atoms existing onthe bottom. Thus, on the bottom of the contact hole 104 a, a reformedlayer (oxidized region) 104 b where the carbon component has beeneliminated is formed. At this time, a volatile reaction product such asHCN or CN is generated. By this reformation, the composition of thebottom portion (reformed layer 104 b) of the contact hole 104 a is closeto the composition of SiO₂. This means that the bottom of the contacthole 104 a is nicely etched with the etching species such as CF_(x)contained in the plasma, while a volatile reaction product such as SiF,CO₂, CHF₃, or CH₄ is generated. As a result, the etching rate at thebottom of the contact hole 104 b in the organic/inorganic hybrid film104 is roughly the same as the etching rate at a silicon oxide (SiO₂)film containing no carbon component.

[0164] X-ray photoelectron spectroscopy (XPS) analysis was performed forthe organic/inorganic hybrid film 104 immediately after the depositionthereof and when plasma processing was performed with NH₃/N₂ gas. Theresults of the analysis are as follows.

[0165] FIGS. 5(a), 5(b), 6(a), and 6(b) show the results of XPS analysisof the four types (film types a, b, c, and d) of the organic/inorganichybrid film 104 that were formed under different deposition conditions.In each graph, the x-axis represents the distance in the depth direction(corresponding to the sputtering time) and the y-axis represents theatomic concentration. FIGS. 4(a), 4(b), 5(a), and 5(b) show the resultsof film types a, b, c, and d, respectively. The compositions of the fourfilm types a, b, c, and d are as follows: the silicon component occupiesabout 30%, the oxygen component about 25 to 45%, the carbon componentabout 17 to 37%, and the nitrogen component about 5% or less. From theXPS analysis results and in consideration of the material gas for filmformation, it is presumed that SiC, SiN, and CH_(x) (x=1 to 3) arecaptured in the network of SiO_(x) (x=1 to 3) where the amount of CH_(x)captured is the largest.

[0166]FIG. 7 shows the relationship between the distance in the depthdirection and the atomic concentration for the film type c shown in FIG.6(a) (containing about 30% of each of the silicon component, the carboncomponent, and the oxygen component, and about 5% of the nitrogencomponent) of the organic/inorganic hybrid film 104 observed when plasmaprocessing was performed using plasma of a mixed gas of ammonia gas andnitrogen gas. As is found from FIG. 7, in the surface portion of theorganic/inorganic hybrid film 104 (portion having a depth of about 20 nmfrom the surface), the oxygen component increases to about 65% while thecarbon component decreases to 5% or less, with the silicon component andthe nitrogen component being kept unchanged. From these results, it isfound that the surface portion of the organic/inorganic hybrid film 104was reformed to have a composition close to that of a silicon oxide(SiO₂) film. Also found is that it is only the surface portion of theorganic/inorganic hybrid film 104 that was reformed with the otherportion thereof being kept non-reformed. Therefore, the specificdielectric constant of the organic/inorganic hybrid film 104 remainslow.

[0167] Hereinafter, the etching gas used for the plasma etching methodwill be described.

[0168] Normally, a main etching gas used for plasma etching of a SiO₂film is a CF gas such as CF₄, C₂F₆, C₂F₄, C₃F₆, C₃F₆, C₄F₆, C₄F₈(straight-chain or cyclic), and C₅F₈ (straight-chain or cyclic). A CHFgas such as CHF₃, CH₂F₂, and CH₃F is also used as a main etching gas oran added gas for plasma etching of the SiO₂ film. In general, any ofthese main etching gases is seldom used singularly or in combinationwith other main etching gases only. Instead, a rare gas (He, Ar, Ne, Kr,Xe, etc.) or O₂ gas is often mixed in the main etching gas. The rare gasis mixed for the purposes of diluting the etching gas, increasing thedischarge rate of the gas in the reaction chamber, and controlling theelectron temperature of the plasma, among others. The O₂ gas is oftenadded for the purpose of removing a polymer film appropriately in thecase that the polymer film may possibly be excessively formed on thewafer surface if only the main etching gas is used. Moreover, CO, CO₂,SO, SO₂, and the like may sometimes be added for the purpose ofimproving the etching ability of a resist pattern as an etching mask forthe SiO₂ film or improving the etching selection ratio of the SiO₂ filmto an underlying film (ratio of the etching rate of the SiO₂ film tothat of an underlying film). By using a gas obtained by combining thegases described above, it is possible to perform suitable etching forthe SiO₂ film that meets the requirements in the process.

[0169] However, any of combinations of gasses described above fails tosuitably etch an organic/inorganic hybrid SiO₂ film. In order to attainetching suitable for an organic/inorganic hybrid SiO₂ film, the etchingmethod of the present invention is inevitably required.

[0170] The etching method of the first embodiment is based on themechanism that etching is performed by repeating alternately in amicroscopic sense (simultaneously in a macroscopic sense) the processesof: reacting an organic component in an organic/inorganic hybrid filmwith nitrogen-containing molecules on the etching reaction surface ofthe organic/inorganic hybrid film and removing a reaction product; andreacting silicon in the organic/inorganic hybrid film with a gascontaining fluorine and carbon and removing a reaction product.

[0171] As described above, as the etching gas used in the firstembodiment, usable is a gas including a main etching gas capable ofetching a SiO₂ film, which is either a gas containing fluorine andcarbon or a gas containing fluorine, carbon, and hydrogen, into which agas containing a nitrogen component is mixed.

[0172] Examples of the gas containing a nitrogen component mixed in themain etching gas include a single gas of nitrogen (N₂), compounds ofnitrogen and hydrogen (NH₃, N₂H₂, etc.), compounds of nitrogen andoxygen (NO, NO₂, N₂O, N₂O₃, etc.), compounds of nitrogen and carbon(C₂N₂, etc.), compounds of nitrogen and fluorine (NF₃, etc.), andcompounds of nitrogen, oxygen, and fluorine (NOF, NO₂F, etc.).

[0173] The compounds of nitrogen and carbon (C₂N₂, etc.), with which theeffect of the present invention is obtainable, are however notpreferable from the standpoint of safety because in the event of gasleakage, the compounds will react with water in the atmosphere andgenerate prussic acid gas (HCN).

[0174] As described in the “SUMMARY OF THE INVENTION”, JapaneseLaid-Open Patent Publication No. 9-263050 describes a method for etchingan “inorganic” SiO₂ film containing fluoride or fluoride/nitrogen withan etching gas that is a mixture of a fluorocarbon gas and a gas of acompound of nitrogen and hydrogen.

[0175] The feature of the etching method described in Japanese Laid-OpenPatent Publication No. 9-263050 is as follows. By generating plasma fromthe etching gas that is a mixture of a fluorocarbon gas and a gas of acompound of nitrogen and hydrogen, fluorine dissociated from thefluorocarbon and fluorine released from the fluorine-containing“inorganic” SiO₂ film are bound with nitrogen or hydrogen. In this way,excessive generation of fluorine is suppressed. By this mechanism, theratio of the etching rate of the “inorganic” SiO₂ film to that of thephotoresist mask or the underlying substrate is improved, that is, theetching selection ratio is improved.

[0176] As is apparent from the above, the mechanism utilized by theetching method for an organic/inorganic hybrid film of the presentinvention is completely different from the etching method disclosed inJapanese Laid-Open Patent Publication No. 9-263050.

[0177] From the standpoint of eliminating the carbon component form thesurface portion of the organic/inorganic hybrid SiO₂ film, the reactionon the etching reaction surface of the organic/inorganic hybrid SiO₂film is facilitated more efficiently by adding both nitrogen gas andhydrogen gas than by adding only nitrogen gas. The reason is that byadding nitrogen gas and hydrogen gas, there occurs a reaction changingcarbon to HCN or the like that is highly volatile and therefore carbonis easily eliminated. In other words, carbon can be eliminated moreefficiently by adding nitrogen gas and hydrogen gas to the etching gasthan by adding only nitrogen gas. Thus, by adding hydrogen gas to theetching gas containing fluorine, carbon and nitrogen, it is possible toenhance the efficiency of elimination of the carbon component.

[0178] From the standpoint of enabling supply of nitrogen and hydrogenin the plasma, the effect obtained by mixing a nitrogen-containing gasand hydrogen gas separately into the etching gas containing fluorine andcarbon is substantially the same as the effect obtained by mixing a gasof a compound of nitrogen and hydrogen into the etching gas.

[0179] As described above, the ability of eliminating the carboncomponent increases by mixing nitrogen and hydrogen into a gascontaining fluorine and carbon in the etching method for anorganic/inorganic hybrid film. Note that there is a danger of causingexplosion and the like if hydrogen gas and oxygen gas are simultaneouslyadded to a gas containing fluorine, carbon and nitrogen. Therefore, ifimportance is put on safety, no oxygen gas should preferably be addedwhen hydrogen gas is added.

[0180] The fluorocarbon gas and the hydrofluorocarbon gas were usedexemplified above as the etching gas containing fluorine and carbonmainly used for etching of the inorganic SiO₂ film. In the etchingmethod of the present invention, gases that exhibit good properties inetching of the inorganic SiO₂ film, such as HFE (hydrofluoro-ether) orHFO (hydrofluoro cyclized olefin), may be used as the etching gascontaining fluorine and carbon. These gases have recently receivedattention as etching gases contributing to prevention of global warming.The etching method of the present invention can also be attained bymixing a nitrogen-containing gas into these gases.

[0181] By mixing a gas enabling supply of oxygen in the plasma, such asCO and CO₂, into the etching gas containing fluorine, carbon andnitrogen, the surface portion of the organic/inorganic hybrid film 104can be oxidized or reformed efficiently.

[0182] In the case that the gas containing a nitrogen component isreplaced with oxygen gas, the carbon component existing in the surfaceportion of the organic/inorganic hybrid film 104 reacts with the oxygencomponent, generating carbon monoxide and carbon dioxide. The surfaceportion is therefore oxidized and thus reformed. However, by addingoxygen gas to the etching gas, the etching rate of the resist pattern105 increases, thereby reducing the etching selection ratio of theorganic/inorganic hybrid film 104 to the resist pattern 105. Inaddition, with an increased etching rate, the resist pattern 105 itselfis etched, and thus the size of the openings of the resist pattern 105greatly varies. This makes it difficult to form the fine contact holes104 a through the organic/inorganic hybrid film 104 with high sizeprecision.

[0183] Thus, in the first embodiment, the organic/inorganic hybrid film104 is plasma-etched with an etching gas containing fluoride, carbon andnitrogen. Therefore, the organic/inorganic hybrid film 104 can be etchedat an etching rate roughly equal to that of a silicon oxide film, andyet can maintain the properties thereof such as the specific dielectricconstant and also can secure a good etching selection ratio with respectto the resist pattern 105.

[0184] The reformation of the surface portion of the organic/inorganichybrid film 104 includes removing carbon atoms or hydrogen atoms fromthe surface portion to obtain a composition close to that of the SiO₂film. This is inevitably accompanied by increase of the specificdielectric constant.

[0185] To avoid the above problem, during the etching for the entireorganic/inorganic hybrid film 104, it is preferable to use an etchinggas containing fluorine, carbon and nitrogen before the etching entersits final stage. At the final stage of the etching, an etching gascontaining fluorine and carbon but containing no nitrogen is preferablyused. In this way, the organic/inorganic hybrid film 104 can be etchedat a high etching rate while the surface portion thereof is beingreformed before the final stage of the etching. At the final stage ofthe etching, the already-reformed surface portion can be etched withoutincreasing the specific dielectric constant. Thus, as the entire etchingprocess, the etching rate can be improved without increasing thespecific dielectric constant.

[0186] (Second Embodiment)

[0187] A plasma etching method of the second embodiment of the presentinvention carried out using the plasma processing apparatus describedabove will be described with reference to FIGS. 1, 8, and 9.

[0188] First, as in the first embodiment, an interconnection layer isformed on a semiconductor substrate. An etching stopper film isdeposited over the entire semiconductor substrate including theinterconnection layer. An organic/inorganic hybrid film represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) is deposited on the etching stopperfilm, and a resist pattern is formed on the organic/inorganic hybridfilm.

[0189] Thereafter, in step SB1 shown in FIG. 8, the resultantsemiconductor substrate is placed in the reaction chamber 10 of theplasma etching apparatus. In step SB2, the semiconductor substrate isfixed to the lower electrode 11.

[0190] In step SB3, a reformation gas and an etching gas are fed intothe reaction chamber 10. The kinds and the ways of feeding of thereformation gas and the etching gas are to be described with referenceto step SB6.

[0191] In step SB4, the first high-frequency power is applied to theplasma induction coil 17 from the first high-frequency source 19, togenerate plasma between the lower electrode 11 and the upper electrode13. Also, the second high-frequency power is applied to the lowerelectrode 11 from the second high-frequency source 21. With thisapplication, the etching species in the plasma are attracted to thesemiconductor substrate 100. As a result, in step SB5, theorganic/inorganic hybrid film is plasma-etched.

[0192] In step SB6, the feeding of the reformation gas and the etchinggas is alternately switched so that the organic/inorganic hybrid film isalternately reformed and etched. specifically, as shown in FIG. 9,first, a nitrogen-containing gas is fed as the reformation gas to reform(oxidize) the surface portion of the organic/inorganic hybrid film. Thefeeding of the nitrogen-containing gas is then stopped, and a CF gas,for example, is fed as the etching gas containing fluorine and carbon toetch the surface portion of the organic/inorganic hybrid film.Thereafter, the reformation process using the nitrogen-containing gasand the etching process using the CF gas are repeated alternately. Notethat in the process of reforming the surface portion of theorganic/inorganic hybrid film, it is possible to reduce the secondhigh-frequency power applied to the lower electrode 11 from the secondhigh-frequency source 21.

[0193] Once the organic/inorganic hybrid film has been etched to apredetermined depth, in step SB7, the application of the high-frequencyvoltages to the upper electrode 13 and the lower electrode 11 and thefeeding of the etching gas are stopped, to finish the etching.

[0194] As described above, the etching method of the second embodimentis based on the mechanism that etching is performed by repeatingalternately in a macroscopic sense the processes of: reacting an organiccomponent in the organic/inorganic hybrid film with nitrogen-containingmolecules on the etching reaction surface of the organic/inorganichybrid film and removing a reaction product; and reacting silicon in theorganic/inorganic hybrid film with a gas containing fluorine and carbonand removing a reaction product. In this etching method, the impetus forthe process of reacting an organic component in the organic/inorganichybrid film with nitrogen-containing molecules is nitrogen and anitrogen compound generated in the plasma from the gas containing anitrogen component. Likewise, the impetus for the process of reactingsilicon in the organic/inorganic hybrid film with the gas containingfluorine and carbon is fluorine and CF molecules generated in the plasmafrom the gas containing fluorine and carbon.

[0195] In view of the above, in the second embodiment, the gascontaining a nitrogen component may be used in the process of reactingan organic component in the organic/inorganic hybrid film withnitrogen-containing molecules, and the etching gas containing fluorineand carbon conventionally used for etching of a SiO₂ film may be used inthe process of reacting silicon in the organic/inorganic hybrid filmwith the gas containing fluorine and carbon.

[0196] In the second embodiment, also, in the process of reacting anorganic component in the organic/inorganic hybrid film withnitrogen-containing molecules, it is effective to use plasma obtained byadding nitrogen and hydrogen. For example, a mixed gas of H₂ and N₂, NH₃gas, or the like is preferably added to the gas containing fluorine andcarbon.

[0197] In the second embodiment, the reformation process using thenitrogen-containing gas (N₂ gas) and the etching process using the gascontaining fluorine and carbon (CF gas) are repeated alternately.Therefore, a carbide generated by reaction between the CF gas and theSiC_(x)H_(y)O_(z) film is prevented from reacting with an nitride as anetching species. As a result, the reformation of the surface portionwith the nitrogen-containing gas is made efficiently, and the etching ofthe reformed surface portion with the CF gas is made efficiently.

[0198] The etching method of the second embodiment is also effective inthe case that the processing conditions are greatly different betweenthe reformation process and the etching process, such as the case thatthe preferred gas pressure for the reformation using thenitrogen-containing gas (N₂ gas) is different from the preferred gaspressure for the etching using the gas containing fluorine and carbon(CF gas).

[0199] As described above, the reformation of the surface portion of theorganic/inorganic hybrid film is accompanied by increase in specificdielectric constant. Therefore, the etching process should preferably bethe final process in the repetition of the reformation process and theetching process. Also, in the final etching process, the reformedportion should preferably be removed to suppress increase in specificdielectric constant.

[0200] Note however that in the case of etching for formation of acontact hole through the organic/inorganic hybrid film on the etchingstopper film, the reformed layer (that is, the bottom of the contacthole) is finally removed. Therefore, no increase of the specificdielectric constant occurs.

[0201] (Third Embodiment)

[0202] A semiconductor device and a fabricating method therefor as thethird embodiment of the present invention will be described withreference to FIG. 10(a).

[0203] As shown in FIG. 10(a), first, an interconnection layer 202 madeof a copper film, an alloy film of copper as a main component, or thelike is embedded in an insulating film 201 deposited on a semiconductorsubstrate 200. Although illustration is omitted in FIG. 10(a), the sidesand the bottom of the interconnection layer 202 are coated with barriermetal for prevention of metal atoms constituting the interconnectionlayer 202 from diffusing into the insulating film 201.

[0204] An etching stopper film 203 is then deposited on the entiresurface of the semiconductor substrate 200 including the interconnectionlayer 202 by plasma CVD, for example. The etching stopper film 203 ismade of a first organic/inorganic hybrid film represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) in which the proportion of the carboncomponent is relatively large.

[0205] Subsequently, an interlayer insulating film 204 is deposited onthe entire surface of the etching stopper film 203 by plasma CVD, forexample. The interlayer insulating film 204 is made of a secondorganic/inorganic hybrid film represented by SiC_(x)H_(y)O_(z) (x>0,y≧0, z>0) in which the proportion of the carbon component is relativelysmall.

[0206] As the film formation gas for deposition of the etching stopperfilm 203 and the interlayer insulating film 204, usable is a mixed gasof a material gas such as tetramethylsilane (Si(CH₃)₄),dimethyl.dimethylsiloxane (Si(CH₃)₂(—O—CH₃)₂), monomethylsilane(SiH₃(CH₃)), or Hexamethyldisiloxane (Si(CH₃)₃—O—Si(CH₃)₃) and anadditive gas such as N₂O. In the third embodiment, a mixed gas ofhexamethyldisiloxane (HMDSO) and N₂O was fed into a CVD apparatus, todeposit the interlayer insulating film 204 on the semiconductorsubstrate 200 that is kept at 300° C.

[0207] The feature of the third embodiment is that the proportion of thecarbon component contained in the first organic/inorganic hybrid filmconstituting the etching stopper film 203 is larger than the proportionof the carbon component contained in the second organic/inorganic hybridfilm constituting the interlayer insulating film 204.

[0208] The proportion of the carbon component in the etching stopperfilm 203 can be made larger than that in the interlayer insulating film204 in the following manner, for example. The same kind of the materialgas (for example, HMDSO) is used as the main component. The proportionof the additive gas (for example, N₂O) contained in the film formationgas for deposition of the etching stopper film 203 is reduced, while theproportion of the additive gas contained in the film formation gas fordeposition of the interlayer insulating film 204 is increased.Alternatively, a film formation gas including a material gas containingan increased amount of the carbon component may be used for depositionof the etching stopper film 203, while a film formation gas including amaterial gas containing a reduced amount of the carbon component may beused for deposition of the interlayer insulating film 204.

[0209] Thereafter, a resist pattern 205 having openings for formation ofcontact holes is formed on the interlayer insulating film 204. Theinterlayer insulating film 204 is then plasma-etched using the resistpattern 205 as a mask.

[0210] The same etching gas and etching conditions as those used in thefirst embodiment are applied for the plasma etching of the interlayerinsulating film 204. That is, an etching gas having a volume flow ratioof:

[0211] C₄F₈: CH₂F₂:Ar:CO:N₂=2:1:10:5:0.5 is fed into the reactionchamber 10 that is kept at a pressure of 2.6 Pa via the gas inlet 14.The first high-frequency power of 1500 W at 13.56 MHz, for example, isapplied to the plasma induction coil 17 from the first high-frequencysource 19, to generate plasma between the lower electrode 11 and theupper electrode 13. Also, the second high-frequency power of 1400 W at 4MHz, for example, is applied to the lower electrode 11 from the secondhigh-frequency source 21, to attract the etching species in the plasmato the semiconductor substrate 100 to thereby enable plasma etching.

[0212] Thus, as in the first embodiment, the etching species such as N₂in the plasma are attracted to the bottom of the contact hole 204 a andreact with carbon atoms or hydrogen atoms existing on the bottom. As aresult, a reformed layer (oxidized region) where the carbon componenthas been eliminated is formed on the bottom of the contact hole 204 a,and thus the reformed bottom of the contact hole 204 b is nicely etchedwith the etching species such as CF_(x) contained in the plasma.

[0213] Once the etching of the interlayer insulating film 204 has beencompleted and the underlying etching stopper film 203 is exposed in thecontact hole 204 a, the etching is blocked due to the following reason.The proportion of the carbon component contained in the etching stopperfilm 203 is larger than the proportion of the carbon component containedin the interlayer insulating film 204 as described above. Therefore,when the etching stopper film 203 is etched as the etching proceeds, anetching reaction gas containing the carbon component is generated,resulting in deposition of a thick polymer film. In addition, the carboncomponent of the etching stopper film 203, as well as an excess of thecarbon component of the polymer film, is accumulated on the etchingstopper film 203, thereby blocking the progress of the etching. Thissharply decreases the etching rate, and thus the etching stops at thesurface of the etching stopper film 203.

[0214] The etching gas contains a fluorine component for cleaving Si—Obonds as described above. This fluorine component in the etching gas isscavenged by the carbon component contained in the etching stopper film203. More specifically, the fluorine contained in the etching gas reactswith a carbide such as a methyl group contained in the etching stopperfilm 203, to produce a fluorocarbon compound. By this reaction, theamount of the fluorine component contained in the etching gas isreduced, and therefore cleaving of the Si—O bonds in the etching stopperfilm 203 becomes less easy. This sharply decreases the etching rate, andthus the etching stops at the surface of the etching stopper film 203.

[0215] Thus, in the third embodiment, the etching stopper film 203 madeof the second organic/inorganic hybrid film having a relatively largeproportion of the carbon component is formed under the interlayerinsulating film 204 made of the first organic/inorganic hybrid filmhaving a relatively small proportion of the carbon component. Such anetching stopper film 203 can serve as the etching stopper for theinterlayer insulating film 204, and moreover can provide a significantlysmall specific dielectric constant compared with the conventionaletching stopper film made of a silicon nitride.

[0216] In the third embodiment, if the etching stopper film 203 containsan oxygen component, the interconnection layer 202 may possibly beoxidized with the oxygen component although slightly. Therefore, whenthe etching stopper film 203 is made of an organic/inorganic hybrid filmrepresented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0), the film is preferablyan insulating film containing no oxygen component (that is, z=0).

[0217] In the third embodiment, the thickness of the etching stopperfilm 203 is preferably about 50 nm when the thickness of the interlayerinsulating film 204 is about 800 nm. By this setting, a sufficientetching selection ratio can be secured for the etching stopper film 203.

[0218] (Modification of the Third Embodiment)

[0219] A semiconductor device and a fabricating method therefor as amodification of the third embodiment of the present invention will bedescribed with reference to FIG. 10(b).

[0220] The feature of the modification of the third embodiment is that,as shown in FIG. 10(b), a protection film 206 made of a silicon nitridefilm, a silicon carbide film, or the like having a thickness of 10 nm,for example, is formed between the interconnection layer 202 and theetching stopper film 203.

[0221] As described above, if the etching stopper film 203 is made of anorganic/inorganic hybrid film containing an oxygen component, theinterconnection layer 202 may possibly be oxidized with the oxygencomponent although slightly.

[0222] In the modification of the third embodiment, the protection layer206 containing no oxygen component is provided between theinterconnection layer 202 and the etching stopper film 203. Theinterconnection layer 202 is therefore prevented from being oxidizedreliably even when the etching stopper film 203 contains an oxygencomponent.

[0223] The thickness of the protection film 206 is so small thatincrease in the specific dielectric constant between the lower and upperinterconnections is prevented even when the protection film 206 has amore or less high specific dielectric constant.

[0224] In the third embodiment including the modification thereof, theinterconnection layer 202 was of an embedded type. In the case that theinterconnection layer 202 is formed by patterning a conductive film,also, the effects of the third embodiment and the modification thereofcan be obtained.

[0225] (Fourth Embodiment)

[0226] A semiconductor device and a fabricating method therefor of thefourth embodiment will be described with reference to FIGS. 11(a) to11(c).

[0227] First, as shown in FIG. 11(a), an interconnection layer 302 madeof a copper film, an alloy film of copper as a main component, or thelike is embedded in an insulating film 301 deposited on a semiconductorsubstrate 300.

[0228] An etching stopper film 303 is then deposited on the entiresurface of the interconnection layer 302 by plasma CVD, for example. Theetching stopper film 303 is made of a first organic/inorganic hybridfilm represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) in which theproportion of the carbon component is largest.

[0229] Subsequently, a lower interlayer insulating film (firstinterlayer insulating film) 304 is deposited on the entire surface ofthe etching stopper film 303 by plasma CVD, for example. The lowerinterlayer insulating film 304 is made of a second organic/inorganichybrid film represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in whichthe proportion of the carbon component is smallest.

[0230] An upper interlayer insulating film (second interlayer insulatingfilm) 305 is then deposited on the entire surface of the lowerinterlayer insulating film 304 by plasma CVD, for example. The upperinterlayer insulating film 305 is made of a third organic/inorganichybrid film represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in whichthe proportion of the carbon component is intermediate.

[0231] As the film formation gas for deposition of the etching stopperfilm 303, the lower interlayer insulating film 304, and the upperinterlayer insulating film 305, usable is a mixed gas of a material gassuch as tetramethylsilane (Si(CH₃)₄), dimethyl.dimethylsiloxane(Si(CH₃)₂(—O—CH₃)₂), monomethylsilane (SiH₃(CH₃)), orHexamethyldisiloxane (Si(CH₃)₃—O—Si(CH₃)₃) and an additive gas such asN₂O. In the fourth embodiment, a mixed gas of hexamethyldisiloxane(HMDSO) and N₂O was used.

[0232] The proportion of the carbon component is made smaller in theorder of the first organic/inorganic hybrid film constituting theetching stopper film 303, the third organic/inorganic hybrid filmconstituting the upper interlayer insulating film 305, and the secondorganic/inorganic hybrid film constituting the lower interlayerinsulating film 304, in the following manner, for example. While thesame kind of the material gas (for example, HMDSO) is used as the maincomponent, the proportion of the additive gas (for example, N₂O)contained in the film formation gas is increased or decreased.Alternatively, a film formation gas including a material gas containingan increased or decreased amount of the carbon component may beselected.

[0233] Thereafter, a resist pattern 306 having openings for formation ofcontact holes is formed on the upper interlayer insulating film 305. Theupper and lower interlayer insulating films 305 and 304 are sequentiallyplasma-etched using the resist pattern 306 as a mask.

[0234] The same etching gas and etching conditions as those used in thefirst embodiment are applied for the plasma etching of the upper andlower interlayer insulating films 305 and 304. That is, an etching gashaving a volume flow ratio of:

[0235] C₄F₈:CH₂F₂:Ar:CO:N₂=2:1:10:5:0.5 is fed into the reaction chamberthat is kept at a pressure of 2.6 Pa, and plasma of the etching gas isgenerated to enable plasma etching.

[0236] Under the above conditions, etching proceeds for the upperinterlayer insulating film 305 in the following manner. The etchingspecies such as N₂ contained in the plasma react with carbon atoms orhydrogen atoms existing on the bottom of the contact hole 307 to reformthe bottom during the etching. Since the upper interlayer insulatingfilm 305 contains the carbon component in an intermediate proportion, anetching reaction gas containing the carbon component is generated in anintermediate amount during the etching of the interlayer insulating film305. This facilitates deposition of a polymer film on the wall and thebottom of the contact hole 307. In addition, the carbon component in theinterlayer insulating film 305 impedes progress of the etching. Theetching rate therefore decreases toward the bottom of the contact hole307. Therefore, the amount of polymer deposited on the wall is greaterthan the amount of progress of the etching toward the bottom. As aresult, as shown in FIG. 11(b), the diameter of the contact hole 307 issmaller toward to the bottom.

[0237] Subsequently, in the plasma etching for the lower interlayerinsulating film 304, etching proceeds in the following manner. Theetching species such as N₂ contained in the plasma react with carbonatoms or hydrogen atoms existing on the bottom of the contact hole 307to reform the bottom during the etching. The deposition of a polymerfilm and the etching proceed competing with each other on the bottom ofthe contact hole 307. However, since the lower interlayer insulatingfilm 304 contains the carbon component in the smallest proportion, thecarbon component contained in an etching reaction gas generated duringthe etching of the interlayer insulating film 304 is small, and thus theamount of the polymer film deposited on the wall and the bottom of thepolymer film deposited on the wall and the bottom of the contact hole307 is small. Moreover, the carbon component on the surface of theinterlayer insulating film 304 at the bottom of the contact hole 307 hasbeen sufficiently eliminated, and thus the etching rate does notdecrease toward the bottom. Therefore, the etching rate at the bottom ofthe contact hole 307 is large, and the amount of the polymer filmdeposited on the wall is sufficiently small. As a result, as shown inFIG. 11(c), the etching proceeds with the diameter of the contact hole307 being kept constant.

[0238] As a result of the above etching process, as shown in FIG. 11(c),the wall of the contact hole 307 expands in a tapered shape near theopening thereof and stands vertical near the bottom thereof. With thisshape of the contact hole, when a conductive film is deposited on theupper interlayer insulating film 305 after removal of the resist pattern306, the contact hole 307 is reliably filled with the conductive film.

[0239] In the fourth embodiment, the proportion of the carbon componentcontained in the upper interlayer insulating film 305 is made largerthan that in the lower interlayer insulating film 304. This makes itpossible to reliably form the contact hole 307 having a wall thatexpands in a tapered shape near the opening and stands vertical near thebottom, without the necessity of changing the etching conditions.

[0240] In the fourth embodiment, also, by adjusting the thicknesses ofthe upper interlayer insulating film 305 and the lower interlayerinsulating film 304, it is possible to reliably control the heights ofthe portion of the contact hole 307 having a tapered wall and theportion thereof having a vertical wall.

[0241] In the fourth embodiment, the proportion of the carbon componentcontained in the lower and upper interlayer insulating films 304 and 305was changed in stages. Alternatively, the proportion of the carboncomponent contained in the organic/inorganic hybrid film may be changedcontinuously.

[0242] In the fourth embodiment, the etching stopper film 303 made ofthe first organic/inorganic hybrid film having the largest proportion ofthe carbon component was provided under the lower interlayer insulatingfilm 304. Alternatively, an etching stopper film made of a siliconnitride film, for example, may be provided.

[0243] (Fifth Embodiment)

[0244] A semiconductor device and a fabricating method therefor of thefifth embodiment will be described with reference to FIGS. 12(a) to12(c).

[0245] First, as shown in FIG. 12(a), an interconnection layer 402 madeof a copper film, an alloy film of copper as a main component, or thelike is embedded in an insulating film 401 deposited on a semiconductorsubstrate 400.

[0246] An etching stopper film 403 is then deposited on the entiresurface of the interconnection layer 402 by plasma CVD, for example. Theetching stopper film 403 is made of a first organic/inorganic hybridfilm represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which theproportion of the carbon component is relatively large.

[0247] Subsequently, an interlayer insulating film 404 is deposited onthe entire surface of the etching stopper film 403 by plasma CVD, forexample. The interlayer insulating film 404 is made of a secondorganic/inorganic hybrid film represented by SiC_(x)H_(y)O_(z) (x>0,y≧0, z>0) in which the proportion of the carbon component is relativelysmall.

[0248] As the film formation gas for deposition of the etching stopperfilm 403 and the interlayer insulating film 404, usable is a mixed gasof a material gas such as tetramethylsilane (Si(CH₃)₄),dimethyl.dimethylsiloxane (Si(CH₃)₂(—O—CH₃)₂), monomethylsilane(SiH₃(CH₃)), or Hexamethyldisiloxane (Si(CH₃)₃—O—Si(CH₃)₃) and anadditive gas such as N₂O. In the fifth embodiment, a mixed gas ofhexamethyldisiloxane (HMDSO) and N₂O was used.

[0249] The proportion of the carbon component in the etching stopperfilm 403 can be made larger than that in the interlayer insulating film404 in the following manner, for example. The same kind of the materialgas (for example, HMDSO) is used as the main component. The proportionof the additive gas (for example, N₂O) contained in the film formationgas for deposition of the etching stopper film 403 is reduced, while theproportion of the additive gas contained in the film formation gas fordeposition of the interlayer insulating film 404 is increased.Alternatively, a film formation gas including a material gas containingan increased amount of the carbon component may be used for depositionof the etching stopper film 403, while a film formation gas including amaterial gas containing a reduced amount of the carbon component may beused for deposition of the interlayer insulating film 404.

[0250] Thereafter, a resist pattern 405 having openings for formation ofcontact holes is formed on the interlayer insulating film 404. Theinterlayer insulating film 404 is then plasma-etched using the resistpattern 405 as a mask.

[0251] Hereinafter, the plasma etching method will be described indetail.

[0252] First, as shown in FIG. 13, first-stage etching is carried out.That is, an etching gas containing fluorine, carbon and nitrogen is fedinto the reaction chamber. High-frequency power is applied to the plasmainduction coil, to generate plasma of the etching gas. The plasma isthen attracted to the semiconductor substrate 400.

[0253] Under the above conditions, etching proceeds in the followingmanner. The etching species such as N₂ contained in the plasma reactwith carbon atoms or hydrogen atoms existing on the bottom of a contacthole 406 (see FIG. 12(b)) to reform the bottom during the etching. Sincethe amount of the N₂ component contained in the etching gas is small,the carbon component of the interlayer insulating film 404 is lesseliminated at the bottom of the contact hole 406. This impedes progressof the etching toward the bottom, and thus the etching rate toward thebottom of the contact hole 406 decreases. Therefore, the amount of apolymer film deposited on the wall is greater than the amount ofprogress of the etching toward the bottom, and thus, as shown in FIG.12(b), the diameter of the contact hole 407 is smaller toward thebottom.

[0254] Subsequently, second-stage etching is carried out as shown inFIG. 13. That is, the added amount of the N₂ gas to the etching gas fedinto the reaction chamber is increased so that the proportion of N₂ isas large as that in the first embodiment (volume flow ratio of N₂gas/volume flow ratio of CF gas is relatively large).

[0255] The above etching proceeds while the etching species such as N₂contained in the plasma react with carbon atoms or hydrogen atomsexisting on the bottom of the contact hole 406 thereby reforming thebottom. Since the amount of the N₂ gas contained in the etching gas islarge, the carbon component at the surface of the interlayer insulatingfilm 404 on the bottom of the contact hole 406 has been sufficientlyeliminated. Therefore, the etching rate toward the bottom does notdecrease. In addition, the amount of the polymer film deposited on thewall of the contact hole 406 is sufficiently small. Thus, the etchingproceeds with the diameter of the contact hole 406 being kept constant.

[0256] As a result, as shown in FIG. 12(c), formed is the contact hole406 of which the wall expands in a tapered shape near the opening andstands vertical near the bottom. Therefore, when a conductive film isdeposited on the interlayer insulating film 404 after removal of theresist pattern 405, the contact hole 406 is reliably filled with theconductive film.

[0257] In the fifth embodiment, the amount of the N₂ gas added to theetching gas is increased during the etching. This makes it possible toreliably form the contact hole 406 of which the wall expands in atapered shape near the opening and stands vertical near the bottom,without changing the composition of the interlayer insulating film 404.

[0258] In the fifth embodiment, the added amount of the N₂ gas waschanged in stages. Alternatively, the added amount of the N₂ gas may bechange continuously.

[0259] In the fifth embodiment, the etching stopper film 403 made of thefirst organic/inorganic hybrid film in which the proportion of thecarbon component was relatively Large was formed under the interlayerinsulating film 404. Alternatively, an etching stopper film made of asilicon nitride film, for example, may be provided.

[0260] (Sixth Embodiment)

[0261] A semiconductor device and a fabricating method therefor of thesixth embodiment will be described with reference to FIGS. 14(a) to14(c) and 15(a) to 15(d).

[0262] First, as shown in FIG. 14(a), a lower interconnection 502 madeof a copper film, an alloy film of copper as a main component, or thelike is embedded in an insulating film 501 deposited on a semiconductorsubstrate 500. An etching stopper film 503 having a thickness of 50 nmis then deposited on the entire surface of the lower interconnection502. The etching stopper film 503 is made of a first organic/inorganichybrid film represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) in whichthe proportion of the carbon component is relatively large.

[0263] Subsequently, an interlayer insulating film 504 is deposited onthe etching stopper film 503 by plasma CVD, for example. The interlayerinsulating film 504 is made of a second organic/inorganic hybrid filmrepresented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportionof the carbon component is relatively small.

[0264] As the film formation gas for deposition of the etching stopperfilm 503 and the interlayer insulating film 504, usable is a mixed gasof a material gas such as tetramethylsilane (Si(CH₃)₄),dimethyl.dimethylsiloxane (Si(CH₃)₂(—O—CH₃)₂), monomethylsilane(SiH₃(CH₃)), or Hexamethyldisiloxane (Si(CH₃)₃—O—Si(CH₃)₃) and anadditive gas such as N₂O.

[0265] The proportion of the carbon component in the etching stopperfilm 503 can be made larger than that in the interlayer insulating film504 in the following manner, for example. The same kind of the materialgas (for example, HMDSO) is used as the main component. The proportionof the additive gas (for example N₂O) contained in the film formationgas for deposition of the etching stopper film 503 is reduced, while theproportion of the additive gas contained in the film formation gas fordeposition of the interlayer insulating film 504 is increased.Alternatively, a film formation gas including a material gas containingan increased amount of the carbon component may be used for depositionof the etching stopper film 503, while a film formation gas including amaterial gas containing a reduced amount of the carbon component may beused for deposition of the interlayer insulating film 504.

[0266] Subsequently, a CMP stopper film 505 made of a silicon nitridefilm, for example, is deposited on the interlayer insulating film 504. Aresist pattern 506 having openings for formation of contact holes isformed on the CMP stopper film 505. The CMP stopper film 505 is thenetched using the resist pattern 506 as a mask, so that the openings ofthe resist pattern 506 are transferred to the CMP stopper film 505.

[0267] Referring to FIG. 14(b), the interlayer insulating film 504 isplasma-etched using the resist pattern 506 as a mask.

[0268] The conditions of this plasma etching are substantially the sameas those used in the first embodiment. That is, the etching gascontaining fluorine, carbon and nitrogen is fed into the reactionchamber, and high-frequency power is applied to the plasma inductioncoil to generate plasma of the etching gas.

[0269] Under the above conditions, the etching proceeds in the followingmanner. The etching species such as N₂ contained in the plasma reactwith carbon atoms or hydrogen atoms existing on the bottom of a contacthole 507 to reform the bottom during the etching. That is, the bottom(reformed layer) of the contact hole 507 has a composition close to thatof SiO₂, and therefore is nicely etched with the etching species such asCF_(x) contained in the plasma.

[0270] Referring to FIG. 14(c), the resist pattern 506 is removed.Referring to FIG. 15(a), the etching stopper film 503 is etched usingthe CMP stopper film 505 having openings as a mask. By this etching, theportion of the etching stopper film 503 exposed in the contact hole 507is removed. Since the etching stopper film 503 is over-etched, a shallowconcave portion is formed at the surface of the lower interconnection502.

[0271] Referring to FIG. 15(b), a metal film 508 made of a copper film,a tungsten film, or the like is deposited on the entire surface of theCMP stopper film 505. The portion of the metal film 508 exposed on theCMP stopper film 505 is then removed by CMP, to form a plug 508A made ofthe metal film 508 as shown in FIG. 15(c). A dishing phenomenon occursat the surface of the plug 508A, so that the surface of the plug 508A isrecessed by a depth roughly equal to the thickness of the CMP stopperfilm 505.

[0272] Referring to FIG. 15(d), when the CMP stopper film 505 is removedby etching, the surface of the plug 508A is flat and flush with thesurface of the interlayer insulating film 504. In the case of amultilayer interconnection structure, the flatness of upperinterconnections can be improved.

[0273] If no dishing phenomenon occurs at the surface of the plug 508A,or if the thickness of the CMP stopper film 505 is larger than thedishing amount, the surface portion of the plug 508A protrudes from theinterlayer insulating film 504 after the removal of the CMP stopper film505. Such a protrusion may be used as an alignment mark in an alignmentprocess for formation of upper interconnections if the flatness of theresultant upper interconnections is within a permissible range.

[0274] In the sixth embodiment, the contact hole 507 can be reliablyformed through the interlayer insulating film 504 made of theorganic/inorganic hybrid film having a low specific dielectric constant.In addition, CMP can be performed nicely for the interlayer insulatingfilm 504 made of an organic/inorganic hybrid film considered poor in CMPresistance because the interlayer insulating film 504 is protected withthe CMP stopper film 505 during the CMP process.

[0275] Moreover, the etching stopper film 503 made of theorganic/inorganic hybrid film having a larger proportion of the carboncomponent is formed under the interlayer insulating film 504. Thisetching stopper film 503, which serves as the etching stopper for theinterlayer insulating film 504, is significantly small in specificdielectric constant compared with the conventional etching stopper filmmade of a silicon nitride film.

[0276] (Seventh Embodiment)

[0277] A semiconductor device and a fabricating method therefor of theseventh embodiment of the present invention will be described withreference to FIGS. 16(a) to 16(c), 17(a) to 17(c), and 18(a) to 18(d).

[0278] First, as shown in FIG. 16(a), a lower interconnection 602 madeof a copper film, an alloy film of copper as a main component, or thelike is embedded in an insulating film 601 deposited on a semiconductorsubstrate 600. An etching stopper film 603 having a thickness of 50 nmis then deposited on the entire surface of the lower interconnection602. The etching stopper film 603 is made of a first organic/inorganichybrid film represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in whichthe proportion of the carbon component is relatively large.

[0279] Subsequently, an interlayer insulating film 604 is deposited onthe etching stopper film 603 by plasma CVD, for example. The interlayerinsulating film 604 is made of a second organic/inorganic hybrid filmrepresented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportionof the carbon component is relatively small.

[0280] As the film formation gas for deposition of the etching stopperfilm 603 and the interlayer insulating film 604, usable is a mixed gasof a material gas such as tetramethylsilane (Si(CH₃)₄),dimethyl.dimethylsiloxane (Si(CH₃)₂(—O—CH₃)₂), monomethylsilane(SiH₃(CH₃)), or Hexamethyldisiloxane (Si(CH₃)₃O—Si(CH₃)₃) and anadditive gas such as N₂O.

[0281] The proportion of the carbon component in the etching stopperfilm 603 can be made larger than that in the interlayer insulating film604 in the following manner, for example. The same kind of the materialgas (for example, HMDSO) is used as the main component. The proportionof the additive gas (for example N₂O) contained in the film formationgas for deposition of the etching stopper film 603 is reduced, while theproportion of the additive gas contained in the film formation gas fordeposition of the interlayer insulating film 604 is increased.Alternatively, a film formation gas including a material gas containingan increased amount of the carbon component may be used for depositionof the etching stopper film 603, while a film formation gas including amaterial gas containing a reduced amount of the carbon component may beused for deposition of the interlayer insulating film 604.

[0282] Subsequently, a CMP stopper film 605 made of a silicon nitridefilm, for example, is deposited on the interlayer insulating film 604. Afirst resist pattern 606 having openings for formation of contact holesis formed on the CMP stopper film 605. The CMP stopper film 605 is thenetched using the first resist pattern 606 as a mask, so that theopenings of the first resist pattern 606 are transferred to the CMPstopper film 605.

[0283] Referring to FIG. 16(b), the interlayer insulating film 604 isplasma-etched using the first resist pattern 606 as a mask.

[0284] The conditions of this plasma etching are substantially the sameas those used in the first embodiment. That is, the etching gascontaining fluorine, carbon and nitrogen is fed into the reactionchamber, and high-frequency power is applied to the plasma inductioncoil to generate plasma of the etching gas.

[0285] Under the above conditions, the etching proceeds in the followingmanner. The etching species such as N₂ contained in the plasma reactwith carbon atoms or hydrogen atoms existing on the bottom of a contacthole 607 to reform the bottom during the etching. That is, the bottom(reformed layer) of the contact hole 607 has a composition close to thatof SiO₂, and therefore is nicely etched with the etching species such asCF_(x) contained in the plasma.

[0286] After the first resist pattern 606 is removed as shown in FIG.16(c), a second resist pattern 608 having openings for formation ofinterconnection grooves is formed on the CMP stopper film 605 as shownin FIG. 17(a).

[0287] Using the second resist pattern 608 as a mask, the CMP stopperfilm 605 and then the interlayer insulating film 604 are sequentiallyetched, to form an interconnection groove 609 communicating with thecontact hole 607 in the interlayer insulating film 604 as shown in FIG.17(b). The conditions for the etching for formation of theinterconnection groove 609 in the interlayer insulating film 604 are thesame as those for formation of the contact hole 607 through theinterlayer insulating film 604.

[0288] After the second resist pattern 608 is removed as shown in FIG.17(c), the portion of the etching stopper film 603 exposed in thecontact hole 607 is removed as shown in FIG. 18(a).

[0289] Referring to FIG. 18(b), a metal film 610 made of a copper film,a tungsten film, or the like is deposited on the entire surface of theCMP stopper film 605. The portion of the metal film 610 exposed on theCMP stopper film 605 is then removed by CMP, to form a plug 610A and anupper interconnection 610B made of the metal film 610 simultaneously asshown in FIG. 18(c).

[0290] Referring to FIG. 18(d), when the CMP stopper film 605 is removedby etching, the surface of the upper interconnection 610B is flat andflush with the surface of the interlayer insulating film 604.

[0291] In the seventh embodiment, the contact hole 607 and theinterconnection groove 609 can be reliably formed in the interlayerinsulating film 604 made of an organic/inorganic hybrid film having alow specific dielectric constant. In addition, CMP can be performednicely for the interlayer insulating film 604 made of anorganic/inorganic hybrid film considered poor in CMP resistance, becausethe interlayer insulating film 604 is protected with the CMP stopperfilm 605 during the CMP process.

[0292] Moreover, the etching stopper film 603 made of theorganic/inorganic hybrid film having a larger proportion of the carboncomponent is formed under the interlayer insulating film 604. Thisetching stopper film 603, which serves as the etching stopper for theinterlayer insulating film 604, is significantly small in specificdielectric constant compared with the conventional etching stopper filmmade of a silicon nitride film.

[0293] (Eighth Embodiment)

[0294] A semiconductor device and a fabricating method therefor of theeighth embodiment will be described with reference to FIGS. 19(a) to19(c) and 20(a) to 20(d).

[0295] First, a lower interconnection 702 made of a copper film, analloy film of copper as a main component, or the like is embedded in aninsulating film 701 deposited on a semiconductor substrate 700. Anetching stopper film 703 having a thickness of 50 nm is then depositedon the entire surface of the lower interconnection 702. The etchingstopper film 703 is made of an insulating film represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportion of the carboncomponent is relatively large.

[0296] Subsequently, an interlayer insulating film 704 is deposited onthe etching stopper film 703 by plasma CVD, for example. The interlayerinsulating film 704 is made of an organic/inorganic hybrid filmrepresented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportionof the carbon component is relatively small.

[0297] As the film formation gas for deposition of the etching stopperfilm 703 and the interlayer insulating film 704, usable is a mixed gasof a material gas such as tetramethylsilane (Si(CH₃)₄),dimethyl.dimethylsiloxane (Si(CH₃)₂(—O—CH₃)₂), monomethylsilane(SiH₃(CH₃)), or Hexamethyldisiloxane (Si(CH₃)₃—O—Si(CH₃)₃) and anadditive gas such as N₂O.

[0298] The proportion of the carbon component in the etching stopperfilm 703 can be made larger than that in the interlayer insulating film704 in the following manner, for example. The same kind of the materialgas (for example, HMDSO) is used as the main component. The proportionof the additive gas (for example N₂O) contained in the film formationgas for deposition of the etching stopper film 703 is reduced, while theproportion of the additive gas contained in the film formation gas fordeposition of the interlayer insulating film 704 is increased.Alternatively, a film formation gas including a material gas containingan increased amount of the carbon component may be used for depositionof the etching stopper film 703, while a film formation gas including amaterial gas containing a reduced amount of the carbon component may beused for deposition of the interlayer insulating film 704.

[0299] Thereafter, a silicon oxide film 705 containing no carboncomponent, such as a TEOS film, having a thickness of 5 nm to 10 nm isdeposited on the interlayer insulating film 704 by plasma CVD, forexample. A positive chemical amplification resist material is thenapplied to the silicon oxide film 705, to form a resist film 706.

[0300] The resist film 706 is then patterned by being exposed to lightvia a mask 707. By this pattern exposure, an exposed portion 706 a ofthe resist film 706 is made soluble to a developer by the function ofacid generated from an acid generator, while non-exposed portions 706 bof the resist film 706 remain hard to dissolve in the developer withoutgeneration of acid from an acid generator. During this process, with theexistence of the silicon oxide film 705 containing no carbon componentinterposed between the resist film 706 and the interlayer insulatingfilm 704, acid (H+) generated in the exposed portion 706 a of the resistfilm 706 is prevented from reacting with a carbon component (C)contained in the interlayer insulating film 704, and thus is notdeactivated. It is therefore ensured that the exposed portion 706 a ismade soluble to the developer by the function of acid.

[0301] Thereafter, as shown in FIG. 19(b), the exposed portion 706 a ofthe resist film 706 is removed by being dissolved in the developer, toform a first resist pattern 708 that is composed of the non-exposedportions 706 b of the resist film 706 and has openings for formation ofcontact holes. Since the exposed portion 706 a of the resist film 706has been made soluble to the developer without deactivation of acid asdescribed above, the resultant first resist pattern 708 is excellent inresolution.

[0302] Referring to FIG. 19(c), the opening of the first resist pattern708 is transferred to the silicon oxide film 705, and then theinterlayer insulating film 704 is plasma-etched using the first resistpattern 708 as a mask, to form a contact hole 709 through the interlayerinsulating film 704.

[0303] The conditions of this plasma etching are substantially the sameas those used in the first embodiment. That is, the etching gascontaining fluorine, carbon and nitrogen is fed into the reactionchamber, and high-frequency power is applied to the plasma inductioncoil to generate plasma of the etching gas.

[0304] Under the above-conditions, the etching proceeds in the followingmanner. The etching species such as N₂ contained in the plasma reactwith carbon atoms or hydrogen atoms existing on the bottom of a contacthole 709 to reform the bottom during the etching. Therefore, the bottomof the contact hole 709 is nicely etched with the etching species suchas CF_(x) contained in the plasma.

[0305] Referring to FIG. 20(a), before or after removal of the resistpattern 708 with oxygen plasma, the wall of the contact hole 709 isexposed to a nitrogen-containing gas or a gas containing fluoride,carbon and nitrogen, to form a reformed layer 710 on the wall of thecontact hole 709 by eliminating the carbon component from theorganic/inorganic hybrid film.

[0306] Referring to FIG. 20(b), after the removal of the first resistpattern 708, a second resist pattern 711 made of a chemicalamplification resist material having openings for formation ofinterconnection grooves is formed on the silicon oxide film 705. Withthe existence of the silicon oxide film 705 having no carbon componentinterposed between the chemical amplification resist film and theinterlayer insulating film 704, and the formation of the reformed layer710 containing no carbon component on the wall of the contact hole 709,acid generated in an exposed portion of the resist film is preventedfrom being deactivated. Thus, the resultant second resist pattern 711 isexcellent in resolution.

[0307] Referring to FIG. 20(c), the opening of the second resist pattern711 is transferred to the silicon oxide film 705, and then theinterlayer insulating film 704 is plasma-etched using the second resistpattern 711 as a mask, to form an interconnection groove 712 in theinterlayer insulating film 704.

[0308] The conditions for the above etching are the same as those usedin the first embodiment. That is, the etching gas containing fluorine,carbon and nitrogen is fed into the reaction chamber, and high-frequencypower is applied to the plasma induction coil to generate plasma of theetching gas.

[0309] Under the above conditions, the etching proceeds in the followingmanner. The etching species such as N₂ contained in the plasma reactwith carbon atoms or hydrogen atoms existing on the bottom of theinterconnection groove 712 to reform the bottom during the etching.Therefore, the bottom of the interconnection groove 712 is nicely etchedwith the etching species such as CF_(x) contained in the plasma.

[0310] Thereafter, although illustration is omitted, the followingprocesses are carried out as in the seventh embodiment. After removal ofthe second resist pattern 711, the portion of the etching stopper film703 exposed in the contact hole 709 is removed. Before or after theremoval of the resist pattern 711, the reformed layer 710 may be removedby oxide film etching. Thereafter, a metal film made of a copper film ora tungsten film is deposited on the entire surface of the silicon oxidefilm 705. The portion of the metal film exposed on the silicon oxidefilm 705 is then removed by CMP, to obtain multilayer interconnectionshaving a dual damascene structure.

[0311] In the eighth embodiment, the resist film 706 made of a positivechemical amplification resist material was used. When a resist film madeof a negative chemical amplification resist material is used, also,deactivation of acid in the exposed portion of the resist film can beprevented by interposing the silicon oxide film 705 containing no carboncomponent between the interlayer insulating film 704 and the negativeresist film.

[0312] In the case that a reflection prevention film is provided by CVDat a position lower than the resist film 706 shown in FIG. 19(a), it ispreferable to form the reflection prevention film on the interlayerinsulating film 704 and then the silicon oxide film 705 on thereflection prevention film. By this structure, it is possible to preventdeactivation of acid in the resist film 706 caused due to the existenceof the reflection prevention film based on a mechanism, different fromthat in the case of the organic/inorganic hybrid film, that works whenthe underlying layer is an alkaline film or a film other than theorganic/inorganic hybrid film that easily binds with H^(+.)

[0313] (First Modification of the Eighth Embodiment)

[0314] In the eighth embodiment, the silicon oxide film 705 containingno carbon component was deposited on the interlayer insulating film 704made of the organic/inorganic hybrid film. In the first modification ofthe eighth embodiment, the silicon oxide film 705 containing no carboncomponent is formed on the interlayer insulating film 704 by reformingthe surface portion of the interlayer insulating film 704 made of theorganic/inorganic hybrid film.

[0315] First, as in the eighth embodiment, the interlayer insulatingfilm 704 made of the organic/inorganic hybrid film is deposited.

[0316] The interlayer insulating film 704 is then etched back with anetching gas containing fluorine and carbon. At the final stage of thisetch-back process, an etching gas containing fluorine, carbon andnitrogen is fed and plasma is generated from the etching gas. Theetching species such as N₂ contained in the plasma are attracted to thesurface portion of the interlayer insulating film 704 and react withcarbon atoms or hydrogen atoms existing on the surface portion. Thus,the surface portion of the interlayer insulating film 704 is reformed bythe elimination of the carbon component, forming the silicon oxide film705.

[0317] Thereafter, a chemical amplification resist material is appliedto the silicon oxide film 705 formed on the interlayer insulating film704, to form the resist film 706, as in the eighth embodiment. Theresist film 706 is then subjected to pattern exposure, and the exposedportion 706 a of the resist film 706 is removed with a developer, toform the first resist pattern 708.

[0318] By the above method, the silicon oxide film 705 containing nocarbon component exists between the resist film 706 and the interlayerinsulating film 704. Therefore, as in the eighth embodiment,deactivation of acid generated in the exposed portion 706 a of theresist film 706 is prevented. It is therefore ensured that the exposedportion 706 a is made soluble to the developer by the function of acid.

[0319] (Second Modification of the Eighth Embodiment)

[0320] A semiconductor device and a fabricating method therefor of thesecond modification of the eighth embodiment will be described withreference to FIGS. 21(a) to 21(c).

[0321] First, as in the eighth embodiment, the interlayer insulatingfilm 704 is plasma-etched using the first resist pattern 708 as a mask,to form the contact hole 709 through the interlayer insulating film 704(see FIG. 19(c)). The reformed layer 710 is then formed as shown in FIG.20(a). Thereafter, the first resist pattern 708 is removed by ashingwith oxygen plasma.

[0322] Thereafter, a chemical amplification resist material is appliedto the silicon oxide film 705, to form a resist film. The resist film isthen subjected to pattern exposure and development, to form the secondresist pattern 711 having openings for formation of interconnectiongrooves as shown in FIG. 21(a). During this process, the chemicalamplification resist material is also deposited in the contact hole 709.In the resist film deposited in the contact hole 709, acid generated dueto the pattern exposure is deactivated by the carbon component from theetching stopper film 703. Therefore, the resist film on the bottom ofthe contact hole 709 is left behind after the removal of the exposedportion of the resist film with the developer, forming a protection film711 a made of the chemical amplification resist material in which acidhas been deactivated.

[0323] The opening of the second resist pattern 711 is transferred tothe silicon oxide film 705, and then the interlayer insulating film 704is plasma-etched using the second resist pattern 711 as a mask to forman interconnection groove 712 in the interlayer insulating film 704 asshown in FIG. 21(b).

[0324] The conditions for the above etching are the same as those usedin the first embodiment. That is, the etching gas containing fluorine,carbon and nitrogen is fed into the reaction chamber, and high-frequencypower is applied to the plasma induction coil to generate plasma of theetching gas. Under the above conditions, the etching proceeds in thefollowing manner. The etching species such as N₂ contained in the plasmareact with carbon atoms or hydrogen atoms existing on the bottom of theinterconnection groove 712 to reform the bottom during the etching.Therefore, the bottom of the interconnection groove 712 is nicely etchedwith the etching species such as CF_(x) contained in the plasma.

[0325] The interlayer insulating film 704 is subjected to two times ofplasma etching, one for formation of the contact hole 709 and the otherfor formation of the interconnection groove 712. Therefore, the portionof the etching stopper film 703 exposed in the contact hole 709 maypossibly be extremely thinned or even completely lost (see FIG. 20(c)).Therefore, during the ashing of the second resist pattern 711 withoxygen plasma, the lower interconnection 702 may be exposed to theoxygen plasma forming a naturally oxidized film on the surface of thelower interconnection 702. This may increase the contact resistancebetween the plug made of a conductive film filled in the contact hole709 and the lower interconnection 702.

[0326] In the second modification of the eighth embodiment, the plasmaetching for formation of the interconnection groove 712 is carried outwith the protection film 711 a made of the acid-deactivated chemicalamplification resist material existing on the bottom of the contact hole709. The etching stopper film 703 is therefore exposed to plasma etchingonly once, and thus the portion of the etching stopper film 703 exposedin the contact hole 709 is prevented from being excessively thinned.

[0327] For the above reason, as shown in FIG. 21(c), when the secondresist pattern 711 is removed by ashing with oxygen plasma, the lowerinterconnection 702 is prevented from being exposed to the oxygenplasma. This prevents formation of a naturally oxidized film on thesurface of the lower interconnection 702, and thus prevents increase inthe contact resistance between the plug made of a conductive film filledin the contact hole 709 and the lower interconnection 702.

[0328] Moreover, since the etching stopper film 703 is exposed to plasmaetching only once, the etching stopper film 703 having a small thicknesscan be used. Thus, a material that deactivates a resist, such as anorganic/inorganic hybrid film, can be used as the etching stopper film703. Since the thickness of the etching stopper film 703 can be small,also, the specific dielectric constant between the lower and upperinterconnections can be reduced. In addition, the thickness of theinterlayer insulating film can be reduced, and thus the variation inthickness can be minimized.

What is claimed is:
 1. An etching method for plasma-etching anorganic/inorganic hybrid film represented by SiC_(x)H_(y)O_(z) (x>0,y≧0, z>0), comprising the step of: plasma-etching the organic/inorganichybrid film while eliminating a carbon component from a surface portionof the organic/inorganic hybrid film.
 2. The etching method of claim 1,wherein the plasma etching is performed with an etching gas containingfluorine, carbon and nitrogen.
 3. The etching method of claim 2, whereinthe etching gas contains CO or CO_(2.)
 4. An etching method forplasma-etching an organic/inorganic hybrid film represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0), comprising repeating alternately afirst step of eliminating a carbon compound from a surface portion ofthe organic/inorganic hybrid film and a second step of plasma-etchingthe surface portion from which the carbon compound has been eliminated.5. The etching method of claim 4, wherein the first step is performedwith a gas containing nitrogen, and the second step is performed with anetching gas containing fluorine and carbon.
 6. The etching method ofclaim 5, wherein the gas containing nitrogen is a mixed gas of hydrogenand nitrogen or ammonia gas.
 7. A fabricating method for a semiconductordevice, comprising the steps of: depositing an etching stopper film onan interconnection layer formed on a substrate, the etching stopper filmbeing represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which theproportion of carbon atoms with respect to silicon atoms is relativelylarge; depositing an interlayer insulating film on the etching stopperfilm, the interlayer insulating film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportion of carbonatoms with respect to silicon atoms is relatively small; and forming acontact hole through the interlayer insulating film by plasma-etchingthe interlayer insulating film.
 8. The fabricating method for asemiconductor device of claim 7, wherein the plasma etching is performedwith an etching gas containing fluorine, carbon and nitrogen.
 9. Afabricating method for a semiconductor device, comprising the steps of:depositing a first interlayer insulating film on an interconnectionlayer formed on a substrate, the first interlayer insulating film beingrepresented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportionof carbon atoms with respect to silicon atoms is relatively small;depositing a second interlayer insulating film on the etching stopperfilm, the second interlayer insulating film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportion of carbonatoms with respect to silicon atoms is relatively large; andplasma-etching the second interlayer insulating film and the firstinterlayer insulating film sequentially, to form a first opening throughthe second interlayer insulating film, the diameter of the first openingbeing smaller toward the bottom end, and a second opening through thefirst interlayer insulating film, the wall of the second opening beingvertical to the bottom surface.
 10. The fabricating method for asemiconductor device of claim 9, wherein the plasma etching is performedwith an etching gas containing fluorine, carbon and nitrogen.
 11. Afabricating method for a semiconductor device, comprising the steps of:depositing an interlayer insulating film represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) on a substrate; performing firstplasma-etching for the interlayer insulating film while blocking orsuppressing a carbon component from being eliminated from a surfaceportion of the interlayer insulating film, to form a first opening inthe interlayer insulating film, the diameter of the first opening beingsmaller toward the bottom end; and performing second plasma-etching forthe interlayer insulating film while facilitating elimination of thecarbon component from the surface portion of the interlayer insulatingfilm, to form a second opening under the first opening in the interlayerinsulating film, the wall of the first opening being vertical to thebottom surface.
 12. The fabricating method for a semiconductor device ofclaim 11, wherein the first plasma-etching is performed with a firstetching gas containing fluorine, carbon and nitrogen in which theproportion of nitrogen is relatively small, and the secondplasma-etching is performed with a second etching gas containingfluorine, carbon and nitrogen in which the proportion of nitrogen isrelatively large.
 13. A fabricating method for a semiconductor device,comprising the steps of: depositing an interlayer insulating filmrepresented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) on a substrate; forminga silicon oxide film containing no carbon component on a top surface ora surface portion of the interlayer insulating film; forming a resistfilm made of a chemical amplification resist material on the siliconoxide film; and subjecting the resist film to pattern exposure anddevelopment to form a resist pattern made of the resist film.
 14. Afabricating method for a semiconductor device of claim 13, wherein thesilicon oxide film is formed by eliminating a carbon component from thesurface portion of the interlayer insulating film.
 15. A fabricatingmethod for a semiconductor device, comprising the steps of: depositingan etching stopper film on an interconnection layer formed on asubstrate, and then depositing an interlayer insulating film representedby SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) on the etching stopper film;forming a contact hole through the interlayer insulating film; forming aresist pattern made of a chemical amplification resist material, theresist pattern having an opening for formation of an interconnectiongroove, and also forming a protection film made of the chemicalamplification resist material on the bottom of the contact hole forprotecting the etching stopper film; and plasma-etching the interlayerinsulating film using the resist pattern, to form the interconnectiongroove in the interlayer insulating film.
 16. A fabricating method for asemiconductor device, comprising the steps of: depositing an etchingstopper film on an interconnection layer formed on a substrate, theetching stopper film being represented by SiC_(x)H_(y)O_(z) (x>0, y≧0,z≧0) in which the proportion of carbon atoms with respect to siliconatoms is relatively large; depositing an interlayer insulating film onthe etching stopper film, the interlayer insulating film beingrepresented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportionof carbon atoms with respect to silicon atoms is relatively small;depositing a CMP stopper film on the interlayer insulating film; forminga resist pattern having an opening for formation of a contact hole onthe CMP stopper film; transferring the opening of the resist pattern tothe CMP stopper film, and then plasma-etching the interlayer insulatingfilm while eliminating a carbon component from a surface portion of theinterlayer insulating film, to form a contact hole through theinterlayer insulating film; after removal of the resist pattern,depositing a conductive film on the CMP stopper film to fill the contacthole with the conductive film; and removing a portion of the conductivefilm exposed on the CMP stopper film by CMP, to form a plug made of theconductive film.
 17. A fabricating method for a semiconductor device,comprising the steps of: depositing an etching stopper film on a lowerinterconnection formed on a substrate, the etching stopper film beingrepresented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportionof carbon atoms with respect to silicon atoms is relatively large;depositing an interlayer insulating film on the etching stopper film,the interlayer insulating film being represented by SiC_(x)H_(y)O_(z)(x>0, y≧0, z>0) in which the proportion of carbon atoms with respect tosilicon atoms is relatively small; depositing a CMP stopper film on theinterlayer insulating film; forming a first resist pattern having anopening for formation of a contact hole on the CMP stopper film;transferring the opening of the first resist pattern to the CMP stopperfilm, and then plasma-etching the interlayer insulating film whileeliminating a carbon component from a surface portion of the secondorganic/inorganic hybrid film, to form the contact hole through theinterlayer insulating film; after removal of the first resist pattern,forming a second resist pattern having an opening for formation of aninterconnection groove on the CMP stopper film; transferring the openingof the second resist pattern to the CMP stopper film, and thenplasma-etching the interlayer insulating film while eliminating a carboncomponent from a surface portion of the interlayer insulating film, toform the interconnection groove in the interlayer insulating film;depositing a conductive film on the CMP stopper film to fill the contacthole and the interconnection groove with the conductive film; andremoving a portion of the conductive film exposed on the CMP stopperfilm by CMP, to form a plug and an upper interconnection made of theconductive film.
 18. A fabricating method for a semiconductor device,comprising: an etching stopper film formed on an interconnection layerformed on a substrate, the etching stopper film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) in which the proportion of carbonatoms with respect to silicon atoms is relatively large; an interlayerinsulating film formed on the etching stopper film, the interlayerinsulating film being represented by SiC_(x)H_(y)O_(z) (x>0, y≧0, z>0)in which the proportion of carbon atoms with respect to silicon atoms isrelatively small; and a contact hole formed through the interlayerinsulating film by plasma-etching.
 19. A semiconductor device,comprising: a first interlayer insulating film deposited on a substrate,the first interlayer insulating film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z≧0) in which the proportion of carbonatoms with respect to silicon atoms is relatively small; a secondinterlayer insulating film deposited on the first interlayer insulatingfilm, the second interlayer insulating film being represented bySiC_(x)H_(y)O_(z) (x>0, y≧0, z>0) in which the proportion of carbonatoms with respect to silicon atoms is relatively large; a first openingformed through the second interlayer insulating film by plasma-etching,the diameter of the first opening being smaller toward the bottom end;and a second opening formed under the first opening through the firstinterlayer insulating film, the wall of the second opening beingvertical to the bottom surface.